#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 k1=k-1;
    long int n =((k1*(k1+1))/2)+1;
    long int num = 1+(n-1)*2;
    long int result=0;
    //int j=0;
    for(int i=0;i<k;i++)
    {
        result = result+num;
        //j=2;
        num=num+2;
    }
    return result;
}

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