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

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

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