/in/foo.cc: In function 'int main()':
/in/foo.cc:145:10: error: reference to 'hash' is ambiguous
   int wz=hash(k);
          ^
/in/foo.cc:120:5: note: candidates are: int hash(int)
 int hash(int x)
     ^
In file included from /usr/include/c++/5/bits/basic_string.h:5471:0,
                 from /usr/include/c++/5/string:52,
                 from /usr/include/c++/5/random:40,
                 from /usr/include/c++/5/bits/stl_algo.h:66,
                 from /usr/include/c++/5/algorithm:62,
                 from /in/foo.cc:4:
/usr/include/c++/5/bits/functional_hash.h:58:12: note:                 template<class _Tp> struct std::hash
     struct hash;
            ^