problem_72.cpp

#include <iostream>

void tree(int d, int n);
long long int found = 0;
int target = 1000000;

void tree(int d, int n) {
	if(d > target)
		return;
	found += 1;
	tree(2*d-n, d);
	tree(2*d+n, d);
	tree(d+2*n, n);
}

int main() {
	tree(2, 1);
	tree(3, 1);
	std::cout << "The answer is " << found << std::endl;
}