View Compilation Error

0_0_13664685_28734.cpp: In function 'int main()':
0_0_13664685_28734.cpp:89:23: error: reference to 'hash' is ambiguous
             int pos = hash(a[i]);
                       ^
0_0_13664685_28734.cpp:35:5: note: candidates are: int hash(int)
 int hash(int x){
     ^
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_bvector.h:1181:0,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/vector:65,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/queue:61,
                 from 0_0_13664685_28734.cpp:2:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/functional_hash.h:58:12: note:                 template<class _Tp> struct std::hash
     struct hash;
            ^