diff --git a/backend/include/engine.h b/backend/include/engine.h
index e96b284..0340655 100644
--- a/backend/include/engine.h
+++ b/backend/include/engine.h
@@ -2,6 +2,7 @@
 #define PROTECTOR_ENGINE_H
 #include <stack>
 #include <string>
+#include <unordered_map>
 #include <vector>
 
 #include "database.h"
@@ -11,40 +12,56 @@ class BookStoreEngineClass {
   UserDataBase user_data_base;
   BookDataBase book_data_base;
   LogDataBase log_data_base;
+  std::unordered_map<std::string, int> login_count;
   bool is_server;
 
  public:
   BookStoreEngineClass() = delete;
   BookStoreEngineClass(std::string __config_dir, bool __is_server);
-  std::vector<std::string> Execute(const std::string &cmd,
-                                   std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteSu(const std::string &cmd,
-                                     std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteLogout(const std::string &cmd,
-                                         std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> Execute(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteSu(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteLogout(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
   std::vector<std::string> ExecuteRegister(
-      const std::string &cmd, std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecutePasswd(const std::string &cmd,
-                                         std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteUserAdd(const std::string &cmd,
-                                          std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteDelete(const std::string &cmd,
-                                         std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteShow(const std::string &cmd,
-                                       std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteBuy(const std::string &cmd,
-                                      std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteSelect(const std::string &cmd,
-                                         std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteMOdify(const std::string &cmd,
-                                         std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteImport(const std::string &cmd,
-                                         std::stack<std::pair<std::string, std::string>> &login_stack);
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecutePasswd(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteUserAdd(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteDelete(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteShow(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteBuy(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteSelect(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteMOdify(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteImport(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
   std::vector<std::string> ExecuteShowFinance(
-      const std::string &cmd, std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteLog(const std::string &cmd,
-                                      std::stack<std::pair<std::string, std::string>> &login_stack);
-  std::vector<std::string> ExecuteReport(const std::string &cmd,
-                                      std::stack<std::pair<std::string, std::string>> &login_stack);
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteLog(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
+  std::vector<std::string> ExecuteReport(
+      const std::string &cmd,
+      std::stack<std::pair<std::string, std::string>> &login_stack);
 };
 #endif  // PROTECTOR_ENGINE_H
\ No newline at end of file
diff --git a/backend/src/builtin-cli.cpp b/backend/src/builtin-cli.cpp
index e2e5281..6679a82 100644
--- a/backend/src/builtin-cli.cpp
+++ b/backend/src/builtin-cli.cpp
@@ -17,9 +17,12 @@ void BookStoreMain(bool is_server, std::string config_dir) {
     std::string cmd;
     while (std::getline(std::cin, cmd)) {
       auto result = std::move(engine.Execute(cmd, login_stack));
+      // debugPrint(cmd);
       for (auto &line : result) {
         std::cout << line << '\n';
+        // debugPrint(line);
       }
+      // debugPrint();
       if (BookStore_ZYM::shut_down) return;
     }
   } else {
diff --git a/backend/src/engine.cpp b/backend/src/engine.cpp
index 9109bda..63d4756 100644
--- a/backend/src/engine.cpp
+++ b/backend/src/engine.cpp
@@ -45,6 +45,10 @@ std::vector<std::string> BookStoreEngineClass::Execute(
   std::string head = "";
   ss >> head;
   if (head == "quit" || head == "exit") {
+    while (login_stack.size()) {
+      login_count[login_stack.top().first]--;
+      login_stack.pop();
+    }
     if (!is_server) BookStore_ZYM::shut_down = true;
     return std::vector<std::string>();
   }
@@ -115,11 +119,13 @@ std::vector<std::string> BookStoreEngineClass::ExecuteSu(
     if (user_data_base.GetPrevilege(user_id) == -1)
       return std::vector<std::string>({"Invalid"});
     login_stack.push(std::make_pair(user_id, ""));
+    login_count[user_id]++;
     return std::vector<std::string>();
   }
   // debugPrint("Examining", user_id, password);
   if (user_data_base.PAM(user_id, password)) {
     login_stack.push(std::make_pair(user_id, ""));
+    login_count[user_id]++;
     return std::vector<std::string>();
   }
   return std::vector<std::string>({"Invalid"});
@@ -129,6 +135,7 @@ std::vector<std::string> BookStoreEngineClass::ExecuteLogout(
     const std::string &cmd,
     std::stack<std::pair<std::string, std::string>> &login_stack) {
   if (login_stack.empty()) return std::vector<std::string>({"Invalid"});
+  login_count[login_stack.top().first]--;
   login_stack.pop();
   return std::vector<std::string>();
 }
@@ -157,6 +164,10 @@ std::vector<std::string> BookStoreEngineClass::ExecutePasswd(
   // debugPrint("begin checing authority");
   if (login_stack.size() > 0 &&
       user_data_base.GetPrevilege(login_stack.top().first) == 7) {
+    if (current_password != "") {
+      if (!user_data_base.PAM(user_id, current_password))
+        return std::vector<std::string>({"Invalid"});
+    }
     user_data_base.ChangePassword(user_id, new_password);
     return std::vector<std::string>();
   }
@@ -178,7 +189,7 @@ std::vector<std::string> BookStoreEngineClass::ExecuteUserAdd(
   int privilege;
   if (!CommandUseraddLexer(cmd, user_id, password, privilege, user_name))
     return std::vector<std::string>({"Invalid"});
-  if (privilege > own_previlege) return std::vector<std::string>({"Invalid"});
+  if (privilege >= own_previlege) return std::vector<std::string>({"Invalid"});
   if (user_data_base.GetPrevilege(user_id) != -1)
     return std::vector<std::string>({"Invalid"});
   user_data_base.AddUser(user_id, password, user_name, privilege);
@@ -194,6 +205,7 @@ std::vector<std::string> BookStoreEngineClass::ExecuteDelete(
   std::string user_id;
   if (!CommandDeleteLexer(cmd, user_id))
     return std::vector<std::string>({"Invalid"});
+  if (login_count[user_id] > 0) return std::vector<std::string>({"Invalid"});
   if (user_data_base.GetPrevilege(user_id) == -1)
     return std::vector<std::string>({"Invalid"});
   user_data_base.DeleteUser(user_id);