/in/foo.cc:13:1: error: reference to 'unordered_map' is ambiguous
 unordered_map<string, bool>Hash;
 ^~~~~~~~~~~~~
In file included from /usr/include/c++/6/tr1/unordered_map:42:0,
                 from /in/foo.cc:2:
/usr/include/c++/6/tr1/unordered_map.h:180:11: note: candidates are: template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> class std::tr1::unordered_map
     class unordered_map
           ^~~~~~~~~~~~~
In file included from /usr/include/c++/6/unordered_map:48:0,
                 from /usr/include/x86_64-linux-gnu/c++/6/bits/stdc++.h:117,
                 from /in/foo.cc:1:
/usr/include/c++/6/bits/unordered_map.h:98:11: note:                 template<class _Key, class _Tp, class _Hash, class _Pred, class _Alloc> class std::unordered_map
     class unordered_map
           ^~~~~~~~~~~~~
/in/foo.cc: In function 'int bfs()':
/in/foo.cc:36:2: error: 'Hash' was not declared in this scope
  Hash[getstring(s)]=1;
  ^~~~
/in/foo.cc:66:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^