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: Accepted)

#include <stdio.h>

int main()
{
  int x, y, z;

  scanf("%d%d", &x, &y);
  if(x > y)
    {
      x = x % y;
      for(z = x; z > 0; z--)
	{
	  if((x % z) == 0 && (y % z) == 0) break;
	}
    }
  else if(x < y)
    {
      y = y % x;
      for(z = y; z > 0; z--)
	{
	  if((x % z) == 0 && (y % z) == 0) break;
	}    
    }
  else z = x; 
  printf("%d\n", z);

  return 0;
}