#include <bits/stdc++.h>
using namespace std;
int main(int argc, const char* argv[]) {
  long long a = 0, b = 0;
  cin >> a >> b;
  if (a == 0 && b == 0) {
    cout << "NO" << endl;
    return 0;
  }
  if (abs(a - b) <= 1) {
    cout << "YES" << endl;
  } else {
    cout << "NO" << endl;
  }
  return 0;
}
