#include <bits/stdc++.h>
const int N = 1e5 + 7;
const int INF = 1e9 + 7;
using namespace std;
int n, i, a, b;
int main() {
  cin >> a >> b;
  if (a == b && a == 0)
    cout << "NO";
  else if (abs(a - b) <= 1)
    cout << "YES";
  else
    cout << "NO";
}
