LightOJ 1325 Distributing Chocolates

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const int p = 100000007;

ll fast_pow(ll x, int n)
{
ll res = 1;
while(n)
{
if(n & 1) res = (res * x) % p;
x = (x * x) % p;
n >>= 1;
}
return res;
}
int solve(int a, int b)
{
int m = ceil(sqrt(p));
map<int,int> M;
ll mid = 1;
for(int i = 0; i < m; i++)
M[mid] = i, mid = (mid * a) % p;
ll t = fast_pow(fast_pow(a, p - 2), m);
for(int i = 0; i < m; i++)
{
if(M.find(b) != M.end()) return i * m + M[b];
b = (b * t) % p;
}
}

int main()
{
int T;
scanf("%d", &T);

for(int ca = 1; ca <= T; ca++)
{
int k, res;
scanf("%d%d", &k, &res);
printf("Case %d: %d\n", ca, solve(k, res));
}
return 0;
}