求助，二分70分

#include "cstdio"
#include "algorithm"
#include "cmath"
#define LL long long
using namespace std;

int in()
{
    char c=getchar();
    int x=0,f=1;
    for(;c<'0' || c>'9';c=getchar())
        if(c=='-') f=-1;
    for(;c>='0' && c<='9';c=getchar())  
        x=(x<<1)+(x<<3)+(c^48);
    return x*f;
}

const int N=100005;
int a[N], b[N];
int m, n, now;

int main()
{
	// freopen("P1678_1.in","r",stdin);
	// freopen("P1678_1.ans","w",stdout);
    m=in(), n=in();
    for(int i=1;i<=m;i++)   
        a[i]=in();//预计录取分数
    for(int i=1;i<=n;i++)
        b[i]=in();//估分成绩
    LL ans=0;
    sort(a+1,a+m+1);
    for(int i=1;i<=n;i++)
    {
        now=lower_bound(a+1,a+1+m,b[i])-a;
        ans+=min(abs(a[now]-b[i]), abs(a[now-1]-b[i]));
    }
    printf("%lld\n", ans);
    return 0;
}