(a*b)%m=(a%m)*(b%m)%m
(a+b)%m=(a%m+b%m)%m
然后。。干它就完了
#include<iostream>
#include<algorithm>
#include<map>
#include<cstring>
#include<vector>
#include<cmath>
#include<cstdio>
using namespace std;
int main(){
long long n,m;
cin>>n>>m;
int out=1;
for(int i=2;i<=n;i++){
out=(out%m)*(i%m)%m;
}
cout<<out;
return 0;
}