#include <stdio.h>

int rec(int n) {
	int a;
	if(n<1) return n;
	else{
		a = n + rec(n-2) + n + rec(n-3) ;
	}
	return a;
}
int main(void) {
	// your code goes here
	printf("%d",rec(6));
	return 0;
}