/in/foo.cc: In function 'void dfs(int)':
/in/foo.cc:20:23: error: 'memset' was not declared in this scope
   memset(w,0,sizeof(w));
                       ^
/in/foo.cc:32:18: error: 'max' was not declared in this scope
    ans=max(ans,an);
                  ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:45:2: error: 'cin' was not declared in this scope
  cin>>n>>m>>v;
  ^~~
/in/foo.cc:51:2: error: 'cout' was not declared in this scope
  cout<<ans<<endl;
  ^~~~
/in/foo.cc:51:13: error: 'endl' was not declared in this scope
  cout<<ans<<endl;
             ^~~~