#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) {
    int a, b;
    cin >> a >> b;
    if (a == 0 && b == 0)
      cout << "NO\n";
    else if (a == b || a + 1 == b || b + 1 == a) {
      cout << "YES\n";
    } else {
      cout << "NO\n";
    }
  }
  return 0;
}
