using AtCoder;
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Runtime.CompilerServices;
class Program
{
    static string ReadLine() => Console.ReadLine().Trim();
    static int ReadInt() => int.Parse(ReadLine());
    static long ReadLong() => long.Parse(ReadLine());
    static int[] ReadIntArray() { string str = ReadLine(); return str != "" ? str.Split().Select(_ => int.Parse(_)).ToArray() : new int[0]; }
    static long[] ReadLongArray() { string str = ReadLine(); return str != "" ? str.Split().Select(_ => long.Parse(_)).ToArray() : new long[0]; }

    static (int a, int b) ReadInt2() { int[] vs = ReadIntArray(); return (a: vs[0], b: vs[1]); }
    static (int a, int b, int c) ReadInt3() { int[] vs = ReadIntArray(); return (a: vs[0], b: vs[1], c: vs[2]); }
    static (int a, int b, int c, int d) ReadInt4() { int[] vs = ReadIntArray(); return (a: vs[0], b: vs[1], c: vs[2], d: vs[3]); }
    static (long a, long b) ReadLong2() { long[] vs = ReadLongArray(); return (a: vs[0], b: vs[1]); }
    static (long a, long b, long c) ReadLong3() { long[] vs = ReadLongArray(); return (a: vs[0], b: vs[1], c: vs[2]); }
    static (long a, long b, long c, long d) ReadLong4() { long[] vs = ReadLongArray(); return (a: vs[0], b: vs[1], c: vs[2], d: vs[3]); }

    static void Main()
    {
        SourceExpander.Expander.Expand();

        (int N, int M) = ReadInt2();
        int[] S = ReadIntArray().OrderBy(_ => _).ToArray();
        int[] T = ReadIntArray();

        int ok = 0;
        int ng = T.Length + 1;
        int cnt = StlFunction.BinarySearch(ok, ng, mid => Check(mid));
        Console.WriteLine(GetScore(cnt));

        bool Check(int cnt)
        {
            int[] T2 = T.Take(cnt).OrderBy(_ => _).ToArray();
            Queue<int> q = new Queue<int>(S);
            foreach (int v in T2)
            {
                while (q.Count > 0 && q.Peek() < v)
                    q.Dequeue();
                if (q.Count > 0)
                    q.Dequeue();
                else
                    return false;
            }
            return true;
        }

        long GetScore(int cnt)
        {
            long ans = 0;
            int[] T2 = T.Take(cnt).OrderBy(_ => _).ToArray();
            Queue<int> q = new Queue<int>(S);
            foreach (int v in T2)
            {
                while (q.Count > 0 && q.Peek() < v)
                    q.Dequeue();
                if (q.Count > 0)
                {
                    int d = q.Dequeue();
                    ans = Math.Max(ans, d - v);
                }
                else
                    return 0;
            }
            return ans;
        }
    }
}

#region Expanded by https://github.com/kzrnm/SourceExpander
namespace AtCoder{public static class StlFunction{public struct NextPermutationEnumerator<T>:IEnumerator<T[]>,IEnumerable<T[]>where T:IComparable<T>{internal readonly IEnumerable<T>_orig;internal NextPermutationEnumerator(IEnumerable<T>orig){_orig=orig;Current=null;}public T[]Current{get;private set;}[MethodImpl(256)]public bool MoveNext(){if(Current==null){Current=_orig.ToArray();return true;}return NextPermutation(Current);}public void Reset()=>Current=null;object IEnumerator.Current=>Current;void IDisposable.Dispose(){}[MethodImpl(256)]public NextPermutationEnumerator<T>GetEnumerator()=>this;IEnumerator<T[]>IEnumerable<T[]>.GetEnumerator()=>this;IEnumerator IEnumerable.GetEnumerator()=>this;}[MethodImpl(256)]public static bool NextPermutation<T>(T[]array)where T:IComparable<T> =>NextPermutation(array.AsSpan());[MethodImpl(256)]public static bool NextPermutation<T>(Span<T>span)where T:IComparable<T>{int i;for(i=span.Length-2;i>=0;i--)if(span[i].CompareTo(span[i+1])<0)break;if(i<0)return false;int j;for(j=span.Length-1;j>=0;j--)if(span[i].CompareTo(span[j])<0)break;(span[i],span[j])=(span[j],span[i]);span.Slice(i+1,span.Length-i-1).Reverse();return true;}[MethodImpl(256)]public static NextPermutationEnumerator<T>Permutations<T>(IEnumerable<T>orig)where T:IComparable<T> =>new NextPermutationEnumerator<T>(orig);private struct DefaultComparer<T>:IComparer<T>where T:IComparable<T>{[MethodImpl(256)]public int Compare(T x,T y)=>x.CompareTo(y);}[MethodImpl(256)]public static int BinarySearch(int ok,int ng,Predicate<int>Ok){while(Math.Abs(ok-ng)>1){var m=(ok+ng)>>1;if(Ok(m))ok=m;else ng=m;}return ok;}[MethodImpl(256)]public static long BinarySearch(long ok,long ng,Predicate<long>Ok){while(Math.Abs(ok-ng)>1){var m=(ok+ng)>>1;if(Ok(m))ok=m;else ng=m;}return ok;}}}
namespace SourceExpander{public class Expander{[Conditional("EXP")]public static void Expand(string inputFilePath=null,string outputFilePath=null,bool ignoreAnyError=true){}public static string ExpandString(string inputFilePath=null,bool ignoreAnyError=true){return "";}}}
#endregion Expanded by https://github.com/kzrnm/SourceExpander