模板 欧拉定理

#include<iostream>
#include<string>
#include<cmath>
#include<cstring>
#include<vector>
#include<map>
#include<set>
#include<algorithm>
#include<queue>
#include<stack>
#include<list>
#include<sstream>
#include<cstdio>
#define INF 0x3f3f3f3f
const int maxn = 1e6 + 5;
const double PI = acos(-1.0);
typedef long long ll;
typedef unsigned long long ull;
using namespace std;

ll a, b, m;

inline ll read(ll m) {
    register ll x = 0, f = 0;
    char ch = getchar();
    while (!isdigit(ch)) ch = getchar();
    while (isdigit(ch)) {
        x = x * 10 + ch - '0';
        if (x >= m) f = 1;
        x %= m, ch = getchar();
    }
    return x + (f == 1 ? m : 0);
}

ll euler_phi(ll n) {
    ll m = ll(sqrt(n + 0.5));
    ll ans = n;
    for (int i = 2; i <= m; i++) {
        if (n % i == 0) {
            ans = ans / i * (i - 1);
            while (n % i == 0) n /= i;
        }
    }
    if (n > 1) ans = ans / n * (n - 1);
    return ans;
}

ll quickPower(ll a, ll b, ll m) {   //计算a的b次方
    ll ans = 1;
    ll base = a;
    while (b) {
        if (b & 1) {
            ans *= base;
            ans %= m;
        }
        base *= base;
        base %= m;
        b >>= 1;   //注意是b>>=1 not b>>1
    }
    return ans;
}

int main() {
    scanf("%lld%lld", &a, &m);
    b = read(euler_phi(m));
    printf("%lld\n", quickPower(a, b, m));
    return 0;
}