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>
#include <math.h>

int main(void) {

	int a,b;
	int c,i,div;

	scanf("%d %d",&a,&b);
	if(a < b){
		c = a;
		a = b;
		b = c;
	}else if(a == b){
		printf("%d\n",a);
		return 0;
	}
	else {}

	for(div=a%b;div>0;div--){
		if(a % div == 0 && b % div == 0) break;
		else {}
	}
	printf("%d\n",div);
	
	return 0;
}