#include <bits/stdc++.h>
using namespace std;
int main() {
  int n1, n2;
  cin >> n1 >> n2;
  if (n1 == 0 && n2 == 0) {
    cout << "NO";
    return 0;
  }
  int r = abs(n1 - n2);
  if (r >= 2)
    cout << "NO";
  else
    cout << "YES";
  return 0;
}
