#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    long i=1,j,c=0,sum;
    while(i<k){
        c+=i;
        i++;
    }
    j=(c*2)+1,sum=0;
    for(i=j;i<j+(k*2)-1;i+=2){
        sum+=i;
    }
    return sum;
}

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