#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 a, s;
    
    a = k * (k - 1) + 1;
    s = a;
    
    while (k > 1) {
        a += 2;
        s += a;
        k--;
    }
    
    return s;
}

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