using System;
using System.Collections.Generic;
using System.Collections;
using System.Collections.Specialized;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.IO;
using System.Reflection;
using static System.Math;
using System.Numerics;
using System.Threading;
using System.Runtime.CompilerServices;
using System.Diagnostics;
//using nint=System.Int32;
static class Program{
	const long inf=long.MaxValue>>1;
	const int mod=(int)1e9+7;//998244353;
	static void Main(){
		Sc sc=new Sc();
		var (n,m)=sc.Tp2<int>();
		var a=sc.Ia3(mod<<1);
		var b=sc.Ia2;
		b[0]=-mod;
		var dp=new long[m+1][];
		dp[0]=new long[]{0,inf};
		for(int i = 1,l=0,r=0;i<=m;i++) {
			dp[i]=new long[]{inf,inf};
			var br=false;
			var bl=false;
			while(a[r]<b[i]){
				r++;
				br=true;
			}
			while(a[l+1]<b[i]){
				l++;
				bl=true;
			}
			if(!bl&&b[i]>a[l]){dp[i][0]=dp[i-1][0]+b[i]-b[i-1];}
			if(b[i]>a[l]){dp[i][0]=Min(dp[i][0],Min(dp[i-1][0],dp[i-1][1])+b[i]-a[l]);}
			if(!br&&b[i]<a[r]){dp[i][1]=dp[i-1][1];}
			if(b[i]<a[r]){dp[i][1]=Min(dp[i][1],Min(dp[i-1][0],dp[i-1][1])+a[r]-b[i]);}
		}
		Console.WriteLine("{0}",dp[m].Min());
	}
}

public class Sc{
	public int I{get{return int.Parse(Console.ReadLine());}}
	public long L{get{return long.Parse(Console.ReadLine());}}
	public double D{get{return double.Parse(Console.ReadLine());}}
	public string S{get{return Console.ReadLine();}}
	public int[] Ia{get{return Array.ConvertAll(Console.ReadLine().Split(),int.Parse);}}
	public long[] La{get{return Array.ConvertAll(Console.ReadLine().Split(),long.Parse);}}
	public double[] Da{get{return Array.ConvertAll(Console.ReadLine().Split(),double.Parse);}}
	public string[] Sa{get{return Console.ReadLine().Split();}}
	public object[] Oa{get{return Console.ReadLine().Split();}}
	public int[] Ia2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),int.Parse);}}
	public int[] Ia3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),int.Parse);}
	public int[] Ia3(int a){return Array.ConvertAll((Console.ReadLine()+" "+a.ToString()).Split(),int.Parse);}
	public long[] La2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),long.Parse);}}
	public long[] La3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),long.Parse);}
	public long[] La3(int a){return Array.ConvertAll((Console.ReadLine()+" "+a.ToString()).Split(),long.Parse);}
	public double[] Da2{get{return Array.ConvertAll(("0 "+Console.ReadLine()+" 0").Split(),double.Parse);}}
	public double[] Da3(string a,string b){return Array.ConvertAll((a+Console.ReadLine()+b).Split(),double.Parse);}
	public T[] Arr<T>(int n,Func<T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f();}return a;}
	public T[] Arr<T>(int n,Func<int,T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i);}return a;}
	public T[] Arr<T>(int n,Func<string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(Console.ReadLine().Split());}return a;}
	public T[] Arr<T>(int n,Func<int,string[],T> f){var a=new T[n];for(int i=0;i<n;i++){a[i]=f(i,Console.ReadLine().Split());}return a;}
	public (T,T) Tp2<T>(){var s=Console.ReadLine().Split();return (Ct<T>(s[0]),Ct<T>(s[1]));}
	public (T,T,T) Tp3<T>(){var s=Console.ReadLine().Split();return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]));}
	public (T,T,T,T) Tp4<T>(){var s=Console.ReadLine().Split();return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]),Ct<T>(s[3]));}
	public (T,T,T,T,T) Tp5<T>(){var s=Console.ReadLine().Split();return (Ct<T>(s[0]),Ct<T>(s[1]),Ct<T>(s[2]),Ct<T>(s[3]),Ct<T>(s[4]));}
	public (T1,T2) Tp2<T1,T2>(){var s=Console.ReadLine().Split();return (Ct<T1>(s[0]),Ct<T2>(s[1]));}
	public (T1,T1,T2) Tp3<T1,T2>(){var s=Console.ReadLine().Split();return (Ct<T1>(s[0]),Ct<T1>(s[1]),Ct<T2>(s[2]));}
	private T Ct<T>(string s){return (T)Convert.ChangeType(s,typeof(T));}
}