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