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