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