WA,悬关

#include <bits/stdc++.h>
using namespace std;
#define int long long
const int N=1e5+5;
int a[N],b[N];
int m,n,ans=0;
signed main(void)
{
	ios::sync_with_stdio(0);
	cin.tie(0),cout.tie(0);
	cin>>m>>n;
	for(int i=1;i<=m;i++)
		cin>>a[i];
	for(int i=1;i<=n;i++)
		cin>>b[i];
	sort(a+1,a+n+1);
	for(int i=1;i<=n;i++)
	{
		int l=1,r=m,mid;
		while(l<=r)
		{
			mid=(l+r)>>1;
			if(a[mid]>b[i])
				r=mid-1;
			else
				l=mid+1;
		}
		if(m==1) ans+=(a[l]-b[i]);
		else ans+=min(abs(a[l]-b[i]),abs(a[l-1]-b[i]));
	}
	cout<<ans;
	return 0;
}