foo.cc: In function 'int main()':
foo.cc:31:6: warning: 'n2' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<n2;
  ~~~~^~~~
foo.cc:30:8: warning: 'n1' may be used uninitialized in this function [-Wmaybe-uninitialized]
  cout<<n1<<endl;
        ^~

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