#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>
long int getsum(long int x)
{
    return x*(x+1)/2;
}
long int sumOfGroup(int k) {
    // Return the sum of the elements of the k'th group
    long int x=getsum(k);
    long int y=getsum(k-1);
    return getsum(x)*2-x-getsum(y)*2+y;
}

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