大佬求教

#include <bits/stdc++.h>
using namespace std;
int n,m,x,a[1000005];
int find(int x){
    int l=1,r=n;
    while (l<=r){
        int mid=(l+r)/2;
        if (a[mid]==x)
            return mid-1;
        else if (a[mid]>x)
            r=mid-1;
        else
            l=mid+1;
    }
    return -1;
}
int main(){
    cin >> n >> m;
    for (int i = 1;i <= n;i++)  
        cin >> a[i];
    for (int i = 1;i <= m;i++){
        cin >> x;
        cout << find(x) << ' ';
    }
    return 0;
}