foo.cc: In function 'int main()':
foo.cc:15:7: warning: unused variable 'shuchu' [-Wunused-variable]
  char shuchu[2000000];
       ^~~~~~
foo.cc:10:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%[^\n]",a);
     ~~~~~^~~~~~~~~~~~

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