foo.cc: In function 'int main()':
foo.cc:95:3: warning: 'f' may be used uninitialized in this function [-Wmaybe-uninitialized]
  f++;
  ~^~
foo.cc:97:15: warning: 'e' may be used uninitialized in this function [-Wmaybe-uninitialized]
  long long g[f-e];
              ~^~

自豪的采用HydroJudge(https://github.com/hydro-dev/Hydro)进行评测。