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