#include <bits/stdc++.h>
using namespace std;
int n;
int main() {
  int x, y;
  cin >> x >> y;
  if (x + y == 0) {
    cout << "NO\n";
    return 0;
  }
  if (abs(x - y) <= 1)
    cout << "YES\n";
  else
    cout << "NO\n";
  return 0;
}
