foo.cpp: In function 'int rank(int)':
foo.cpp:144:6: warning: unused variable 'p' [-Wunused-variable]
  int p=find(k);
      ^
foo.cpp: In function 'int main()':
foo.cpp:162:23: error: reference to 'rank' is ambiguous
         printf("%d\n",rank(q));
                       ^
foo.cpp:143:5: note: candidates are: int rank(int)
 int rank(int k){
     ^
In file included from c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\bits\move.h:57:0,
                 from c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\bits\stl_pair.h:59,
                 from c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\utility:70,
                 from c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\algorithm:60,
                 from foo.cpp:5:
c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\type_traits:1243:12: note:                 template<class> struct std::rank
     struct rank
            ^