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0_0_17393434_21281.cpp: In function 'double fabs(double)':
0_0_17393434_21281.cpp:9:8: 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++/x86_64-w64-mingw32/bits/stdc++.h:41,
                 from 0_0_17393434_21281.cpp:1:
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)
                               ^