#include <bits/stdc++.h>
#define ll long long

using namespace std;

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

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