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