foo.cc: In function 'int main()':
foo.cc:30:7: warning: unused variable 'i' [-Wunused-variable]
  ll m,i,j;
       ^
foo.cc:30:9: warning: unused variable 'j' [-Wunused-variable]
  ll m,i,j;
         ^
foo.cc: In function 'int dfs(ll)':
foo.cc:26:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^

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