#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 long k) {
    // Return the sum of the elements of the k'th group.
    long long a = (k-1)*k + 1;
    long long b = 0;
    while(k--) {
        b += a;
        a += 2;
    }
    return b;
}

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