#include <bits/stdc++.h>
#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;
const double g = 10.0, eps = 1e-12;
const int N = 1000000 + 10, maxn = 500 + 100, inf = 0x3f3f3f;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int a, b;
  cin >> a >> b;
  if (a == 0 && b == 0) {
    cout << "NO" << endl;
    return 0;
  }
  if (abs(a - b) <= 1)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
  return 0;
}
