#include <bits/stdc++.h>

using namespace std;

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

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