package main

import . "fmt"

func main() {
	var t, r int
	Scan(&t, &r)
	mem := make([][]int, 101)
	id := 0
	for ti := 0; ti < t; ti++ {
		var n int
		Scan(&n)
		for i := 0; i < n; i++ {
			var s int
			Scan(&s)
			id++
			mem[s] = append(mem[s], id*1e4+ti)
		}
		con := []int{}
		for i, ls := range mem {
			for len(ls) >= 3 {
				con = append(con, ls[0]/1e4, ls[1]/1e4)
				con = append(con, ls[0]/1e4, ls[2]/1e4)
				ls = ls[3:]
			}
			mem[i] = ls
		}
		Println(len(con)/2)
		for i := 0; i < len(con); i += 2 {
			Println(con[i], con[i+1])
		}
	}
}