diff --git a/src/advanced.cpp b/src/advanced.cpp
index 637f3f3..3075c59 100644
--- a/src/advanced.cpp
+++ b/src/advanced.cpp
@@ -6,12 +6,35 @@
 #include "client.h"
 #include "server.h"
 
+/**
+ * @brief The implementation of function CheckResult
+ * @details Only for debug. It checks the map_status and orginal map to see if
+ * the result of Gauss-Jordan Elimination is correct.
+ */
+void CheckResult() {
+#define ERROR_IN_RESULT 0
+  using namespace Client;
+  using namespace Server;
+  for (int i = 0; i < rows; i++)
+    for (int j = 0; j < columns; j++) {
+      if ('0' <= visible_map[i][j] && visible_map[i][j] <= '8')
+        assert(map_status[i][j] == 2);
+      if (visible_map[i][j] == '?') assert(map_status[i][j] != 2);
+      if (map_status[i][j] == 2)
+        assert('0' <= visible_map[i][j] && visible_map[i][j] <= '8');
+      if (map_status[i][j] == 0) assert(visible_map[i][j] == '?');
+      if (map_status[i][j] == 1) assert(origin_map[i][j] == '.');
+      if (map_status[i][j] == -1) assert(origin_map[i][j] == 'X');
+    }
+#undef ERROR_IN_RESULT
+}
 /**
  * @brief The implementation of function Execute
  * @details Use it only when trying advanced task. Do NOT modify it before
  * discussing with TA.
  */
 void Execute(int row, int column) {
+  CheckResult();
   std::string str;
   VisitBlock(row, column);
   if (game_state != 0) {
diff --git a/src/autotest.py b/src/autotest.py
new file mode 100755
index 0000000..2225285
--- /dev/null
+++ b/src/autotest.py
@@ -0,0 +1,139 @@
+#!/usr/bin/python3
+import sys
+import os
+import random
+built_in_test_cases = [
+"""10 10
+........X.
+..........
+..........
+......X...
+..........
+.X.......X
+..........
+X........X
+..........
+X....XX...
+0 0""",
+"""10 10
+.....X...X
+.........X
+X..X......
+X.X.......
+..X.......
+..........
+..........
+..........
+..........
+X.........
+0 0""",
+"""10 10
+.XX.......
+...X...XX.
+..........
+...X......
+.X......X.
+..X....X..
+XX....X...
+..X...X...
+..X.X.X.X.
+....X.....
+0 9""",
+"""10 10
+.......X..
+X.....X...
+X...X.....
+...X......
+..........
+.X.X.X....
+..X.X..X..
+.X.X.....X
+....X.....
+.....X....
+4 9""",
+"""20 20
+X...........X.......
+..XX.............X.X
+.X......X.........X.
+....X.X...X...X.....
+....X.X.........X...
+X.XX...........X.X..
+...X.............XX.
+...XX...X..X..X.X...
+...X.X...X...X......
+.............XX.X...
+.X............X.....
+.X..X.........X....X
+X.X.X..X...X..X.....
+.X....X.X......X....
+...X.........X..X...
+...X.X...X..........
+..X.XX.X......XXXX..
+.X.X...............X
+XXX..X....X.XX..X...
+.X...X.XX........X.X
+0 10"""
+]
+mine_rate=0.15
+total_round=0
+win_round=0
+for i in range(0,10):
+	for data in built_in_test_cases:
+		fn=open("tmp/test.in","w")
+		fn.write(data)
+		fn.close()
+		os.system("build/src/client < tmp/test.in > tmp/test.out")
+		fn=open("tmp/test.out","r")
+		lines=fn.readlines()
+		fn.close()
+		print(lines)
+		total_round+=1
+		if lines[0]=='YOU WIN!\n':
+			win_round+=1
+		print("win rate: "+str(win_round/total_round),win_round,total_round)
+
+input("Press Enter to continue...")
+
+while True:
+	# randomly generate n,m in [2,30]
+	n=random.randint(2,30)
+	m=random.randint(2,30)
+	# print(n,m)
+	# randomly generate mine_rate in [0,1]
+	#mine_rate=random.random()
+	# generate a random map
+	map=[]
+	for i in range(n):
+		map.append([])
+		for j in range(m):
+			if random.random()<mine_rate:
+				map[i].append('X')
+			else:
+				map[i].append('.')
+	# generate a random start point with no mine
+	sx=random.randint(0,n-1)
+	sy=random.randint(0,m-1)
+	while map[sx][sy]=='X':
+		sx=random.randint(0,n-1)
+		sy=random.randint(0,m-1)
+	# output the map
+	fn=open("tmp/test.in","w")
+	fn.write(str(n)+" "+str(m)+"\n")
+	for i in range(n):
+		for j in range(m):
+			fn.write(map[i][j])
+		fn.write("\n")
+	fn.write(str(sx)+" "+str(sy))
+	fn.close()
+	# run the program
+	os.system("build/src/client < tmp/test.in > tmp/test.out")
+	# read the output
+	fn=open("tmp/test.out","r")
+	lines=fn.readlines()
+	fn.close()
+	# check the output
+	print(lines)
+	total_round+=1
+	if lines[0]=='YOU WIN!\n':
+		win_round+=1
+	print("win rate: "+str(win_round/total_round),win_round,total_round)
\ No newline at end of file
diff --git a/src/include/client.h b/src/include/client.h
index 71d9c0c..666f3b9 100644
--- a/src/include/client.h
+++ b/src/include/client.h
@@ -290,6 +290,7 @@ void InterpretResult(std::vector<std::vector<double> > equations) {
     assert(vid >= 0);
     assert(vid < variaID_to_position.size());
     std::pair<int, int> pos = variaID_to_position[vid];
+    if (map_status[pos.first][pos.second] != 0) continue;
     if (sol == 0) {
       map_status[pos.first][pos.second] = 1;
       no_mine_block_to_be_clicked.push(pos);