package main

import . "fmt"

func main() {
	var t, r int
	Scan(&t, &r)
	ss:=[]int{}
	for ;t>0;t--{
		var n, s int
		Scan(&n)
		for i:=0;i<n;i++ {
			if i+1<n {
				Scan(&s)
			} else {
				Scanln(&s)
			}
			ss=append(ss,s)
		}
		Println(len(ss)/2)
		for i:=len(ss)/2; i>0; i-- {
			Println(ss[0], ss[1])
			ss=ss[2:]
		}
	}
}