#include <bits/stdc++.h>

using namespace std;

long long int sumOfGroup(long int k) {
    // Return the sum of the elements of the k'th group.
    long s,i,x=0,y=0,sum=0;
    s=(k*(k+1))/2;
   
    long long int p=1+(s-1)*2;
    /*for(i=1;x<s-1;i=i+2)
     x++;
    cout<<i<<" "<<s<<'\n';
    for(int j=i;y<k;j=j-2)
    {sum=sum+j;y++;}
    return sum;
    */
  //  cout<<p<<'\n';
    for(int i=0;i<k;i++)
    {
        sum+=p;
        p-=2;
    }
    return sum;
    
    
    
}

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