#include <bits/stdc++.h>
using namespace std;
const double PI = acos(-1.0);
const int maxn = 1e5 + 5;
const int Inf = 1e9 + 7;
int main() {
  int a, b;
  while (cin >> a >> b) {
    if (a == 0 && b == 0) {
      printf("NO\n");
    } else if (abs(a - b) <= 1) {
      printf("YES\n");
    } else {
      printf("NO\n");
    }
  }
  return 0;
}
