foo.cc: In function 'int main()':
foo.cc:20:10: error: 'cnt' was not declared in this scope
    cout<<cnt;
          ^~~
foo.cc:20:10: note: suggested alternative: 'cut'
    cout<<cnt;
          ^~~
          cut

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