#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) {
    long int s,t1,t2;
    s = (k*(k-1))/2;
    t1 = 2*s+1;
    t2 = t1 + (k-1)*2;
    s = k*(t1+t2);
    s = s/2;
    return s;
}

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