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