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