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