UVa 10223 - How many nodes ?

// UVa 10223 - How many nodes ?

#include <iostream>
#include <map>
using namespace std;

#define integer unsigned long long

int main() {

	map<integer, int> m;
	m[1] = 0;
	integer c = 1;
	for (int n = 0; c < 4294967295; n++) {
		c = (2 * (2 * n + 1) * c) / (n + 2);
		m[c] = n + 1;
	}

	integer n;
	while ((cin >> n) && n)
		cout << m[n] << endl;
	return 0;
}