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

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

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