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