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