题解

#include <iostream>
using namespace std;
int main() {
    int n,ans=0;
    cin >> n;
    for (int i=1;i<=n;i++) {
        int sum=1;
        for (int j=1;j<=i;j++) {
            sum*=j;
        }
        ans+=sum;
    }
    cout <<ans<< endl;
    return 0;                                                                                                                                                                                                  t
}