#include <bits/stdc++.h> using namespace std; long sumOfGroup(int k) { long i; long n,sum=0; n= k*(k-1)/2; for(i=2*n+1;i<=2*(n+k)-1;i+=2) { sum+=i; } return(sum); } int main() { int k; cin >> k; long answer = sumOfGroup(k); cout << answer << endl; return 0; }