delete pics to save space

3.39365.cpp

@@ -0,0 +1,38 @@
+#include<cstdio>
+#include<algorithm>
+#include<map>
+using namespace std;
+typedef long long LL;
+LL a,b,p;
+LL ksm(LL a,LL b,LL p)
+{
+	LL res=1;
+	for(;b;b>>=1,a=a*a%p) if(b&1) res=res*a%p;
+	return res;
+}
+LL solve()
+{
+	map<LL,int> mp;
+	LL m=sqrt(p)+1,c_j=1;
+	for(int i=0;i<m;i++)
+	{
+		if(mp.find(c_j)==mp.end()) mp[c_j]=i;
+		c_j=c_j*a%p;
+	}
+	LL a__m=ksm(a,p-1-m,p),c_i=b;
+	for(int i=0;i<m;i++)
+	{
+		if(mp.find(c_i)!=mp.end()) return i*m+mp[c_i];
+		c_i=c_i*a__m%p;
+	}
+	return -1;
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	scanf("%lld%lld%lld",&a,&b,&p);
+	printf("%lld\n",solve());
+	return 0;
+}