foo.cc: In function 'int main()':
foo.cc:12:8: warning: 's' may be used uninitialized in this function [-Wmaybe-uninitialized]
  printf("%0.2lf",s*1.0);
  ~~~~~~^~~~~~~~~~~~~~~~

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