Seeking greatest common divisor by the method of dividing

Title Description:
Number of consecutive input n groups (2/group), the number of greatest common divisor per group
Input Description: The first line enters an integer n, followed by two integers per line x, y
Output Description: N rows, one number per line, greatest common divisor for x, y
Directly on the code--

1 #include <cstdio> 2  3 using namespace std; 4  5 int n,x,y; 6  7 int gcd (int a,int  {9
      
       int c=a%
       b;10 while (c!=0 {a a= b;13 b= c;14 c=a%}16  return }18 int {scanf ("% D ",&n); (int i=1;i<=n;i++ {scanf ("%d%d ",&x,&y); printf ("%d\n " }27 return 0}            
        

Seeking greatest common divisor by the method of dividing