#include<cstdio>

 #include<cstring>

 #include<algorithm>

 #define MAX(a,b) a>b?a:b

 using namespace std;

 long long ans,hh,tt,mid,a[],b[];

 int i,n,m;

 bool can(long long x)

 {

     int i,now,j=;

     long long xx,yy;

     for (i=;i<=n;i++)

     {

         if (b[j]<a[i])

             xx=a[i]-b[j];

         else

             xx=;

         if (xx>x) return ;

         yy=MAX((x-xx)/,x-xx*);

         while (b[j]<=a[i]+yy&&j<=m)

             j++;

         if (j>m) return ;

     }

     if (j<=m) return ;

     else

         return ;

 }

 int main()

 {

     scanf("%d%d",&n,&m);

     for (i=;i<=n;i++)

         scanf("%I64d",&a[i]);

     for (i=;i<=m;i++)

         scanf("%I64d",&b[i]);

     sort(a+,a++n);

     sort(b+,b++m);

     hh=;tt=;

     while (hh<=tt)

     {

         mid=(hh+tt)>>;

         if (can(mid))

         {

             ans=mid;

             tt=mid-;

         }

         else

             hh=mid+;

     }

     printf("%I64d\n",ans);

 }