#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 k) {
    long i,sum=0,j;
    k=k-1;
    i=(k*(k+1))+1;
    for(j=0;j<k+1;j++){
        sum=sum+i;
        i+=2;
    }
    return sum;
    // Return the sum of the elements of the k'th group.
}

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