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