#include <iostream>
#include <algorithm>

using namespace std;

int main() {
	int x, y;
	cin >> x >> y;

	if (abs(x - y) % 2 == 1) {
		cout << -1 << endl;
		return 0;
	}

	int ans = 0;
	while (x != y) {
		int x2 = x + y;
		int y2 = x - y;

		if (abs(x2 - y2) < abs(x - y)) {
			x = x2;
			y = y2;
		} else {
			swap(x, y);
		}
		ans++;
	}

	cout << ans << endl;
	return 0;
}