#include <bits/stdc++.h>
using namespace std;
const int N = 1e5 + 5;
int n, m, u, v;
int main() {
  int l, r;
  cin >> l >> r;
  if (l == 0 && r == 0) {
    cout << "NO";
    return 0;
  }
  int d = abs(l - r);
  if (d <= 1) {
    cout << "YES";
    return 0;
  }
  cout << "NO";
}
