View Compilation Error

0_0_21168811_8875.cpp: In function 'int main()':
0_0_21168811_8875.cpp:75:3: error: reference to 'plus' is ambiguous
   plus(s1,s2);
   ^
0_0_21168811_8875.cpp:13:6: note: candidates are: void plus(char*, char*)
 void plus(char s1[],char s2[])
      ^
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/string:48:0,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/random:40,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_algo.h:66,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/algorithm:62,
                 from 0_0_21168811_8875.cpp:3:
GCC4.9.2/x86_64-w64-mingw32/include/c++/bits/stl_function.h:167:12: note:                 template<class _Tp> struct std::plus
     struct plus : public binary_function<_Tp, _Tp, _Tp>
            ^