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