#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    long kac = ((k * (k-1)) / 2) + 1;
    long result =0;
    
    for(long j = kac; j < (kac+k) ; j++ ){
        result += ((2*j) -1);        
    }
    return result;
}
int main() {
    long k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}