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