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 gcd(int x, int y) 
{
	int smaller, bigger, divisor, mod_num;
	int i;

	if(x < y) {
		smaller = x;
		bigger = y;
	} else {
		smaller = y;
		bigger = x;
	}
	mod_num = bigger % smaller;
	if(mod_num == 0)
			return smaller;
	for(i = 1; i < mod_num; i++) {
		if(smaller % i == 0 && mod_num % i == 0) 
			divisor = i;
	}
	return divisor;
}

int main(void) 
{
	int x, y;

	scanf("%d", &x);
	scanf("%d", &y);
	printf("%d\n", gcd(x, y));

	return 0;
}