#include <bits/stdc++.h>
using namespace std;
int m;
int f=0;
int main(){
cin>>m;
for(int i=2;i<=m;i++){
	f=f+(i-1)+i-1;
}
cout<<f+1+10/6*m+4;
    return 0;
}
/**************************************************************
	Problem: 1145
	User: wangyousi
	Language: C++
	Result: Wrong Answer
****************************************************************/