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