根据父节点和子节点下标关系保存x和y到根节点路径看是否有交点

import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNextInt()) {
            int x = sc.nextInt();
            int y = sc.nextInt();
            Set<Integer> set = new HashSet<>();
            while (x != 0) {
                set.add(x);
                x /= 2;
            }
            while (y != 0) {
                if (set.contains(y)) {
                    System.out.println(y);
                    break;
                }
                set.add(y);
                y /= 2;
            }
        }
    }
}