刚学java不会优化，求教。

import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a[] = new int[1000001];
		int n,m;
		n = sc.nextInt();
		m = sc.nextInt();
		for(int i = 0;i < n;i ++) a[i] = sc.nextInt();
		
		while(m > 0)
		{
			int x;
			x = sc.nextInt();
			int l = 0,r = n-1;
			while(l < r)
			{
				int mid = (l+r) / 2;
				if(a[mid] >= x) r = mid;
				else l = mid + 1;
			}
			if(a[l] != x) System.out.print("-1 ");
			else System.out.print((l+1) + " ");
			m --;
		}
	}
}