import java.util.Scanner;

public class GCD {
  public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    System.out.print("Enter two positive integers: ");
    int x = in.nextInt();
    int y = in.nextInt();
    System.out.println("You entered " + x + " and " + y);
    while ( x < 1 || y < 1 ) {
      // x and/or y are less than or equal to 0
      System.out.print("Enter two positive integers: ");
      x = in.nextInt();
      y = in.nextInt();
      System.out.println("You entered " + x + " and " + y);
    }
    // x and y are greater than zero
    int a = x;
    int b = y;
    int r = a % b;
    System.out.println("a, b and r are " + a + " " + b + " " + r);
    while ( r != 0 ) {
      // r should be not zero
      a = b;
      b = r;
      r = a % b;
      System.out.println("a, b and r are " + a + " " + b + " " + r);
    }
    // r should be zero
    System.out.println("The gcd of " + x + " and " + y + " is " + b);
  }
}