#include <iostream>
using namespace std;

int main(){
	int n, m;
	cin >> n >> m;
	if(n <= m){
		cout << 1 << endl;
		return 0;
	}
	int a = n, b = 0, count = 0;
	while(true){
		if(a % 2){
			cout << -1 << endl;
			return 0;
		}
		int tmp = a / 2;
		a -= tmp;
		b += tmp;
		count++;
		if(b == n) break;
		if(b % 2){
			cout << -1 << endl;
			return 0;
		}
		tmp = b / 2;
		b -= tmp;
		a += tmp;
	}
	cout << count << endl;
}