#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    if( k == 1 )
        return 1;
    if( k == 2 )
        return 8;    
    
    long v = 1;
    for( int i = 2; i < k; ++i )
        v += i*2;
    v += 2;
    
    long s = 0;
    for( int j = 0; j < k; ++j ) {
        s += v;
        v += 2;
    }
    
    return s;
}

int main() {
    int k;
    cin >> k;
    long answer = sumOfGroup(k);
    cout << answer << endl;
    return 0;
}