#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(int k) {
    int num = 0, sum = 0, start=1;
    for(int i=1; i<=k; i++){
        num = num + i;
    }
    for(int j=1; j<=(num-k+1); j++){
        start = start+2;
    }
    for(int t=1; t<=k; t++){
        sum=sum+start;
    }
    
   
    return sum;
    
}

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