题解 | 礼物清单

#include <iostream>
using namespace std;

const long long MOD = 1000000007LL;

long long mod_pow(long long base, long long exp, long long mod) {
    long long res = 1;
    base %= mod;
    while (exp > 0) {
        if (exp & 1)
            res = (res * base) % mod;
        base = (base * base) % mod;
        exp >>= 1;
    }
    return res;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    long long n, m;
    cin >> n >> m;

    long long pow2 = mod_pow(2, m, MOD);
    long long base = (pow2 - 1 + MOD) % MOD;
    long long ans = mod_pow(base, n, MOD);

    cout << ans << '\n';
    return 0;
}