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(void){
	int x,y,n,temp;
	scanf("%d %d",&x,&y);
	if( x > y){temp=x;x=y;y=temp;}
	if(x==y){printf("%d\n",x);return 0;}
	for(n=y%x;n>=1;n--){
		if(x%n==0 && y%n==0){break;}
	}
	printf("%d\n",n);
	return 0;
}