#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 sum = 0, n = 1, j = 1, i;
    for(i = 1; i < k; i++)
        n += i;
    for(i = 1; j < n; i += 2)
        j++;
    j = 0;
    for(;j < k; i += 2, j++)
        sum += i;
    if(k == 1)
        return 1;
    else
        return sum;
}

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