#include <bits/stdc++.h>
inline int abs(int x) { return x > 0 ? x : (-x); }
signed main() {
  int a, b;
  scanf("%d%d", &a, &b);
  if (!(a || b)) {
    puts("NO");
    return 0;
  }
  puts(abs(a - b) <= 1 ? "YES" : "NO");
  return 0;
}
