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

unsigned long long int sumOfGroup(unsigned long long int k) {
    unsigned long long int l,sum=0,cnt=0;
   l=(k*(k-1))/2;
    unsigned long long int t_n=1+(l)*2;
    unsigned long long int u;
    for(u=t_n;cnt<k;u+=2,cnt++){
        sum+=u;
    }
    return sum;
    // Return the sum of the elements of the k'th group.
}

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