foo.cc: In function 'int main()':
foo.cc:6:14: warning: 'n' is used uninitialized in this function [-Wuninitialized]
  int n,m,mn=n+m; cin>>n>>m;
             ~^~
foo.cc:6:14: warning: 'm' is used uninitialized in this function [-Wuninitialized]

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