#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  int i, j, x, y, n, m;
  cin >> n >> m;
  if (n == m && m == 0)
    cout << "NO" << endl;
  else if (n + 1 == m || n == m || n == m + 1)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
