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