AcWing 97. 约数之和（分治）

传送门

#include 

using namespace std;
const int mod = 9901;
int A, B;

int Qpow(int a, int b) {
    a %= mod;
    int ans = 1;
    while (b) {
        if (b & 1)
            ans = ans * a % mod;
        a = a * a % mod;
        b >>= 1;
    }
    return ans;
}

int solve(int p, int k) {
    if (k == 0)
        return 1;
    if (k & 1)
        return (1 + Qpow(p, (k + 1) / 2)) * solve(p, (k - 1) / 2) % mod;
    else
        return ((1 + Qpow(p, k / 2)) * solve(p, (k - 1) / 2) + Qpow(p, k)) % mod;
}

int main() {
    //freopen("in", "r", stdin);
    cin >> A >> B;
    int res, ans = 1;
    for (int i = 2; i <= A; i++) {
        res = 0;
        while (A % i == 0) {
            res++;
            A /= i;
        }
        if (res)
            ans = ans * solve(i, res * B) % mod;
    }
    if (!A)
        ans = 0;
    cout << ans << endl;
    return 0;
}