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 JAVA (judge verdict: Accepted)

import java.util.Scanner;

public class Main {
    public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int x,y;
    int small,big,a;
    x = scan.nextInt();
    y = scan.nextInt();
    scan.close();
    if(x < y) {
        small = x;
        big = y;
    }
    else {
        big =x;
        small = y;
    }
    while(true){
        a = big%small;
        big = small;
        small = a;
        if(a==0)break;
    }
    System.out.println(big);
    }
}