#include <bits/stdc++.h>

using namespace std;

long func(long a){
    //if(a==1)return 1;
    //return (a+func(a-1));
    return (a*(1+a)/2);
}

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

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