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