#include <bits/stdc++.h>
using namespace std;
const int MAXN = 100005;
const int INF = 1000000009;
int main() {
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(nullptr);
  int a, b;
  cin >> a >> b;
  if ((a || b) && max(a, b) - min(a, b) < 2) {
    cout << "YES";
  } else {
    cout << "NO";
  }
  return 0;
}
