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) {
      int a,b,c,r;
      Scanner  sc =new Scanner(System.in);
      a=sc.nextInt();
      b=sc.nextInt();
      if (a<b) {
          c=a;
          a=b;
          b=c;
      }  
      r=a%b;
while(r!=0){
a=b;
b=r;
r=a%b;
}
System.out.println(b);
    }
}