#if 1 = 1
#else
#error "ignored #else (?)"
#endif

#if true
  banana
#elif false
  apple
  #error "ignored #elif (?)"
#endif

#if false
  earthworm
  #error ""
#elif true
  apricot
#endif

#if false
  cuckoo
  #error ""
#else
  #if false
    egg
    #error ""
  #else
    nest
  #endif
#endif

#define X 3

#if false
  helicopter
  #error ""
#elif false
  ocean
  #error ""
#else
  #if X = 12
    sand
    #error ""
  #elif 4 * X = 12
    sea urchin
  #endif
#endif