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>

int main(void) {

   int x, y, z, d;
   int c = 1;

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

   if (x < y) {
      z = x;
      x = y;
      y = z;
   }

   for (d = y; d >=2; d--) {
     if (y % d == 0 && (x % y) % d == 0 && c < d) {
       c = d;
     }
   }

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

   return 0;
}