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