C++ 代码

#include <iostream>
#include<bits/stdc++.h>
#define ll long long
#define INF 0x3f3f3f3f
const int mod = 1e9 + 7;
const int N = 1e5 + 10;
const int M = 30;
using namespace std;

ll hp[N];
ll dis[N];

int main()
{
    int n;
    cin>>n;
    ll ans=1;
    for(int i=1;i<=n;i++){
        ans*=i;
        while(ans%10==0) ans/=10;
        ans%=1000;
    }
    cout<<ans%10<<endl;
    return 0;
}