View Compilation Error

0_0_28666477_28671.cpp: In function 'int main()':
0_0_28666477_28671.cpp:67:3: error: reference to 'rank' is ambiguous
   rank(n);
   ^
0_0_28666477_28671.cpp:32:6: note: candidates are: void rank(int)
 void rank(int n)
      ^
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/move.h:57:0,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_pair.h:59,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algobase.h:64,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/char_traits.h:39,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ios:40,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/ostream:38,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/iostream:39,
                 from 0_0_28666477_28671.cpp:1:
GCC4.9.2/x86_64-w64-mingw32/include/c++/type_traits:1340:12: note:                 template<class> struct std::rank
     struct rank
            ^