#include <bits/stdc++.h>

using namespace std;

long sumOfGroup(long k) {
    // Return the sum of the elements of the k'th group.
    
    long s=0,t=0;
    
    //if(k==1) return k;
    // else return (3*(k*(k-1))+9);
    
    for(long i=(k*(k-1)+1);t<k;i++)
    { if(i%2==1)
      //{c++;
      //  if(c>(k*(k-1)/2))
        {   t++;
            s=s+i;
        }  //if(t=k) {return s;}
         
      } return s;
    }
//}

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