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