#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.
    long int i,j=0,l,sum;
    for(i=2;i<=k;i++){
        j = j + i;
    }
    l=j-k+1;
    sum=0;
    for(i=l;i<=j;i++){
        sum = sum + 2*i+1;
    }
    return sum; 
}

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