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