#include <bits/stdc++.h>

using namespace std;

long long sumOfGroup(long long k) {
    long long sum=1+(1ll*k*(k-1)),ans=0,cn=0;
    for(long long i=sum;;i+=2){
        //cout<<"i= "<<i<<endl;
        ans+=i;
        cn++;
        if(cn==k) break;
    }
    return ans;
    // Return the sum of the elements of the k'th group.
}

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