View Compilation Error

0_0_24002140_29007.cpp: In function 'int main()':
0_0_24002140_29007.cpp:113:32: error: reference to 'rank' is ambiguous
         else if(opt=='Q') ans+=rank(root(x),y),cnt0++;
                                ^
0_0_24002140_29007.cpp:46:5: note: candidates are: int rank(int, int)
 int rank(int rt,int x)
     ^
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++/utility:70,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/algorithm:60,
                 from 0_0_24002140_29007.cpp:4:
GCC4.9.2/x86_64-w64-mingw32/include/c++/type_traits:1340:12: note:                 template<class> struct std::rank
     struct rank
            ^