poj1845 Sumdiv

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <cmath>

using namespace std;

const int mod = 9901;
long long cnt[100010],wh[100010],tot,ans = 1;
int a,b;

void exgcd(long long a,long long b,long long &x,long long &y)
{
    if (!b)
    {
        x = 1;
        y = 0;
        return;
    }
    exgcd(b,a % b,x,y);
    long long t = x;
    x = y;
    y = t - (a / b) * y;
    return;
}

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

int main()
{    
    scanf("%d%d",&a,&b);
    for (int i = 2; i <= sqrt(a); i++)
    {
        if (a % i == 0)
        {
            wh[++tot] = i;
            while (a % i == 0)
            {
            a /= i;
            cnt[i]++;
            }
        }
    }
    if (a)
    {
        wh[++tot] = a;
        cnt[a]++;
    }
    
    for (int i = 1; i <= tot; i++)
    {
        long long x,y;
        exgcd(wh[i] - 1,mod,x,y);
        ans = (ans * (( qpow(wh[i],cnt[wh[i]] * b + 1) - 1)* x) % mod) % mod;
    }
    printf("%lld\n",ans);
    
    
    return 0;
}