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