#include<bits/stdc++.h>
#define int long long
using namespace std;
int n,m,x[200005],y[200005],lft[200005],rt[200005],a[200005];
bool cmp(int x,int y)
{
	return lft[x]<lft[y];
}
signed main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++) cin>>x[i];
	for(int i=1;i<=m;i++) cin>>y[i];
	sort(y+1,y+m+1);
	for(int i=1;i<=n;i++)
	{
		int l=1,r=m,find=-1;
		while(l<=r)
		{
			int mid=(l+r)/2;
			if(y[mid]<x[i]) find=mid,l=mid+1;
			else r=mid-1; 
		}
		if(find==-1) lft[i]=INT_MAX;
		else lft[i]=abs(x[i]-y[find]);
		l=1,r=m,find=-1;
		while(l<=r)
		{
			int mid=(l+r)/2;
			if(y[mid]>x[i]) find=mid,r=mid-1;
			else l=mid+1;
		}
		if(find==-1) rt[i]=INT_MAX;
		else rt[i]=abs(x[i]-y[find]);
	}
	for(int i=1;i<=n;i++) a[i]=i;
	sort(a+1,a+n+1,cmp);
	int ans=lft[a[n]],now=0;
	for(int i=n;i>=1;i--)
	{
		now=max(now,rt[a[i]]);
		int cst=min(now,lft[a[i-1]])*2+max(now,lft[a[i-1]]);
		ans=min(ans,cst);
	}
	cout<<ans;
	return 0;
}