#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define IOS ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define debug cout<<"DS"<<endl
int re(){
	int x=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
	while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
	return x*f;
}
void write(int x){
	 if(x<0)putchar('-'),x=-x;
	 if(x>9)write(x/10);
	 putchar(x%10+'0');
}
unordered_map<ll,ll>h;
ll Pow(ll a,ll b,ll p){
	ll res=1;
	while(b){
		if(b&1)res=res*a%p;
		b>>=1;
		a=a*a%p;
	}
	return res;
}
int main(){
	ll a=re();
	ll b=re(),res=a,MOD=9901;
	for(int i=2;i<=res/i;i++){
		while(res%i==0){
			res/=i;
			h[i]++;
		}
	}
	if(res>1)h[res]++;
	ll ans=1;
	for(auto i:h){
		ll p=i.first;
		ll ai=i.second*b+1;
		ll now;
		if(p%MOD==1)now=ai;
		else now = (Pow(p,ai,MOD)-1)*Pow(p-1,MOD-2,MOD)%MOD;
		ans=(ans*now)%MOD;
	}
	cout<<(ans+MOD)%MOD<<endl;
	return 0;
}

这段代码最后一段

	cout<<(ans+MOD)%MOD<<endl;

改成

	cout<<ans<<endl;

就WA 一个点，为什么ans会是负数?