#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(int k) {
    if(k == 1) return 1;
    
    long long ans = 0, st = 1;
    for(int i = 2; i < k; ++i)
        st += (i << 1);
    st += 2;
    
    for(int i = 0; i < k; ++i, st += 2)
        ans += st;
    
    return ans;
}

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