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