上帝与集合的正确用法

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
ll p,a2;
ll euler(ll n) {
    ll res = n;
    for (ll i = 2; i * i <= n; i++) {
        if (n % i == 0) {
            res = res / i * (i - 1);
            while (n % i == 0) n = n / i;
        }
    }
    if (n > 1) res = res / n * (n - 1);
    return res;
}
ll pow_mod(ll a,ll b,ll p) {
    ll res = 1;
    while (b) {
        if (b & 1) res = res * a % p;
        b = b >> 1;
        a = a * a % p;
    }
    return res;
}
ll dfs(ll p) {
    if (p == 1) return 0;
    int np = euler(p);
    return pow_mod(a2, dfs(np) + np, p);
}

int main() {
    int _;
    scanf("%d", &_);
    while (_--) {
        scanf("%lld", &p);
        a2 = 2 % p;
        printf("%lld\n", dfs(p));
    }
}