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