#include <bits/stdc++.h>
using namespace std;
const int MOD = 1e9 + 7;
long long power(long long a, long long b) {
  if (!b) return 1;
  long long temp = (power(a, b / 2)) % MOD;
  if (b & 1)
    return (((temp * temp) % MOD) * a) % MOD;
  else
    return (temp * temp) % MOD;
}
int main() {
  int a, b;
  cin >> a >> b;
  if (a == b && !a) {
    cout << "NO" << endl;
    return 0;
  }
  if ((b - 1) == a || b == a || b == (a - 1))
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
