#include <bits/stdc++.h>
int main() {
  int a, b, r;
  while (scanf("%d %d", &a, &b) == 2) {
    if (a == 0 && b == 0) {
      printf("NO\n");
      continue;
    }
    r = abs(a - b);
    if (r <= 1)
      printf("YES\n");
    else
      printf("NO\n");
  }
  return 0;
}
