package main

// 解説読んだ
// 値決め打ち二分探索、完全に頭から抜け落ちてた…
// 典型中の典型やんけ…

import . "fmt"
import . "os"
import bf "bufio"
import . "sort"

func main() {
	rd:=bf.NewReader(Stdin)
	var n,m int
	Fscan(rd,&n,&m)
	ss := make([]int, n)
	for i:=range ss{
		Fscan(rd,&ss[i])
	}
	ts := make([]int, m)
	for i:=range ts{
		Fscan(rd,&ts[i])
	}
	Ints(ss)
	ttt := make([]int, m)
	p := Search(m, func(i int) bool {
		tt := ttt[:i+1]
		copy(tt, ts[:i+1])
		Ints(tt)
		zz := ss[:]
		for len(tt) > 0 {
			for len(zz) > 0 && zz[0] < tt[0] {
				zz = zz[1:]
			}
			if len(zz) == 0 {
				return true
			}
			zz = zz[1:]
			tt = tt[1:]
		}
		return false
	})
	Ints(ts[:p])
	ans := 0
	for _, t := range ts[:p] {
		for len(ss) > 0 && ss[0] < t {
			ss = ss[1:]
		}
		ans = max(ans, ss[0]-t)
		ss = ss[1:]
	}
	Println(ans)
}