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