package main

import (
	"bufio"
	"fmt"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

	var t int
	if _, err := fmt.Fscan(in, &t); err != nil {
		return
	}

	for tc := 0; tc < t; tc++ {
		var n, k int
		fmt.Fscan(in, &n, &k)

		a := make([]int, n)
		for i := 0; i < n; i++ {
			fmt.Fscan(in, &a[i])
		}

		ans := 0
		for j := 30; j >= 0; j-- {
			zeros := 0
			for i := 0; i < n; i++ {
				if a[i]&(1<<j) == 0 {
					zeros++
				}
			}
			if zeros <= k {
				k -= zeros
				ans |= (1 << j)
			}
		}
		fmt.Fprintln(out, ans)
	}
}