蒟蒻求助

#include<iostream>
#include<cstdio>
using namespace std;
const int N = 1e5+10;
int a[N],n,m;
long long sum;
int find(int x){
    int l = 1,r = n,mid;
    while(l<r){
        mid = (l + r) / 2;
        if(a[mid] >= x){
            r = mid;
        }
        else l = mid+1;
    }   
    if(a[l] == x) return l;
}
int main(){
    scanf("%d %d",&n,&m);
    for(int i = 1;i <= n;i++){
        scanf("%d",&a[i]);
    }
    while(m--){
        int k;
        scanf("%d",&k);
        int ans = find(k);
        sum += min(k - a[ans],a[ans+1]-k);
    }
    printf("%ld\n",sum);

    return 0;
}

麻烦问一下这段代码错在哪里了QAQ 蒟蒻不懂