#include<bits/stdc++.h>
using namespace std;
const int maxn=10000005;
long long ssc[maxn],mark[maxn];
long long n,m;
int main(){
	cin>>m>>n;
	for(int i=1;i<=m;i++)cin>>mark[i];
	for(int i=1;i<=n;i++)cin>>ssc[i];
	long long long ans=0;
	sort(mark+1,mark+m+1);
	for(int i=1;i<=n;i++){
		bool ok=true;
		long long t=ssc[i];
		long long l=1,r=m,mid=0;
		while(l<=r){
			mid=(l+r)/2;
			if(t==mark[mid]){
				break;
			}
			else if(t<mark[mid]){
				r=mid-1;
			}
			else if(t>mark[mid]){
				l=mid+1;
			}
		}
		if(t!=mark[mid]){
			if(mid==n)ans+=min(abs(mark[mid]-t),abs(mark[mid-1]-t));
			else if(mid>=2)ans+=min(abs(mark[mid]-t),min((abs(mark[mid+1]-t)),abs(mark[mid-1]-t)));
			else if(mid==1)ans+=min(abs(mark[mid]-t),abs(mark[mid+1]-t));
		}
	}
	printf("%d",ans);
	return 0;
}