View Compilation Error

0_0_21170535_17202.cpp: In function 'double fabs(double)':
0_0_21170535_17202.cpp:12:8: error: redefinition of 'double fabs(double)'
 double fabs(double a){
        ^
In file included from GCC4.9.2/x86_64-w64-mingw32/include/c++/cmath:44:0,
                 from GCC4.9.2/x86_64-w64-mingw32/include/c++/random:38,
                 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_21170535_17202.cpp:2:
GCC4.9.2/x86_64-w64-mingw32/include/math.h:181:31: note: 'double fabs(double)' previously defined here
   __CRT_INLINE double __cdecl fabs (double x)
                               ^