#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>



long int sumOfGroup(long int k) {
    // Return the sum of the elements of the k'th group.
   long int l=0;
   long int b;
    long int n=0;
        if(k==1)
            return 1;
      else
          n=k*(k-1);
      if(n%2==0)
          n++;
      
   
    
  
    
 
 
    for(long int j=0;j<k;j++)
    {
       
        l=l+n;
        n=n+2;
        
        
        
    }
   
    
    return l;
}
  

int main() {
    long  int k; 
    scanf("%ld", &k);
    long int answer = sumOfGroup(k);
    printf("%ld\n", answer);
    return 0;
}