#include <bits/stdc++.h>
using namespace std;
long long a, b;
int main() {
cin >> a >> b;
if (a < -1)
cout << "no";
else if (a > 1)
cout << "no";
else if (b > 1)
cout << "no";
else if (b < -1)
cout << "no";
else
cout << "yes";
return 0;
}