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

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