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

long int sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group.
     long long int jump=0;
        for(long long int i=1;i<k;i++)
            jump+=i;
        long long int sum  =0;
        sum+=1+2*jump;
        jump = 1+2*jump;
        for(long long int i=1;i<k;i++)
        {jump+=2;
         sum+=jump;
               
        }
        return sum;
}

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