#include <bits/stdc++.h>
using namespace std;
int a, b;
int main() {
  cin >> a >> b;
  if ((abs(a - b) <= 1 && a != 0 && b != 0) || (a == 1 && b == 0) ||
      (a == 0 && b == 1))
    cout << "YES";
  else
    cout << "NO";
}
