题解 | #牛牛学数列4#

#include <bits/stdc++.h> using namespace std; int main() { int n; cin >> n;

int sum = 0;
for( int i = 1 ; i <= n ; i ++ )
{
    for( int j = i ; j <= n ; j ++ )
    {
        sum += i;
    }
}
cout << sum << endl;
return 0;    

}