Problem:
Greatest Common Divisor

Write a program which finds the greatest common divisor of two natural numbers a and b

Input

a and b are given in a line sparated by a single space.

Output

Output the greatest common divisor of a and b.

Constrants

1 ≤ a, b ≤ 109

Hint

You can use the following observation:

For integers x and y, if x ≥ y, then gcd(x, y) = gcd(y, x%y)

Sample Input 1

54 20

Sample Output 1

2

Sample Input 2

147 105

Sample Output 2

21

Solution in C (judge verdict: Time Limit Exceeded)

#include <stdio.h>

main(){
   int x, y;

   scanf("%d %d", &x, &y);

   do {
      if (x >= y){
         x == x % y;
         if (x == y){
            break;
         }
      }

      if (x < y){
         y == y % x;
         if (x == y){
            break;
         }
      }
   } while(x != 1&&y != 1);

   printf("%d\n", y);

   return 0;
}