#include <bits/stdc++.h>
using namespace std;
const int MAX = 1000005;
const int MOD = 1e9 + 7;
int main() {
  int a, b;
  cin >> a >> b;
  if (a == 0 && b == 0) {
    cout << "NO";
    exit(0);
  }
  if (abs(a - b) <= 1)
    cout << "YES";
  else
    cout << "NO";
}
