#include <iostream>
using namespace std;

int main()
{
    long long a,b,c,sum,n;
    cin>>a;
    for(b=1;b<=a;b++){
    c=a-b+1;
    n=b*c;
    sum=sum+n;
    }
    cout<<sum;
    return 0;
}

请问哪错了？ 感谢