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