#include <bits/stdc++.h>
using namespace std;
int main() {
  long long j, k = 0, l, m, z, n;
  cin >> n >> m;
  if (abs(n - m) <= 1 && (n != 0 || m != 0))
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
