#if !defined(_gcd_H)
# define _gcd_H (1)
/*Computes the gcd of two integers, _a and _b.
_a: The first integer of which to compute the gcd.
_b: The second integer of which to compute the gcd.
Return: The non-negative gcd of _a and _b.
If _a and _b are both 0, then 0 is returned, though in reality the
gcd is undefined, as any integer, no matter how large, will divide 0
evenly.*/
int gcd(int _a,int _b);
#endif