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