简单模拟
#include <iostream>
using namespace std;
const int N = 1010;
int ans[N] = {1}, n;
void fanction(int t)
{
int r = 0;
for(int j = 0;j < N;j ++)
{
r = ans[j] * t + r;
ans[j] = r % 10;
r /= 10;
}
}
int main()
{
cin >> n;
for(int i = 1;i <= n;i ++) fanction(i);
for(int i = 0;i < N ;i ++)
if(ans[i]){
cout << ans[i] << endl;
break;
}
return 0;
}