#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    long o=1;
    for(int i=0;i<k;++i)
        for(int j=0;j<i;++j){
            o+=2;
            //cout<<o<<endl;
        }
    
    long ans=o;
    for(int i=0;i<k-1;++i){
        o+=2;
        ans+=o;
        //cout<<o<<endl;
    }
        //ans+=(o+=2);
    
    return ans;
    // Return the sum of the elements of the k'th group.
}

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