#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
    long val=1,ans=0;
    int i;
    for(i=1;i<k;i++){
     val+=i*2;  
    }
    for(i=1;i<=k;i++)
        ans+=val+(i-1)*2;
    return ans;
}

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