#include <stdio.h>
int main(void) {
	// your code goes here
	unsigned long long int i,k,count=0,offset=0,count1=0;
	scanf("%llu",&k);
    unsigned long long int starting_point;
    starting_point=(((k*2)+2)/2)-1;
    starting_point=starting_point*(starting_point+1);
    starting_point-=1;
    for(i=starting_point;count!=k;count++)
    {
        offset+=i;
        i-=2;
        
    }
    printf("%llu",offset);
	return 0;
}