#include <bits/stdc++.h>
using namespace std;
int main() {
  int a, b;
  cin >> a >> b;
  if (abs(a - b) == 1 || abs(a - b) == 0 && (a != 0 && b != 0))
    printf("YES\n");
  else
    printf("NO\n");
  return 0;
}
