求一个简单的解答，不知道为什么全是wa

#include<cstdio>
#include<iostream>
using namespace std;
const int maxn = 1e6 + 8;
int a[maxn];
int find(int l, int r, int x) {
	while (l < r) {
		int mid = (l + r) >> 1;
		if (a[mid] < x) {
			l = mid + 1;
		}
		if (a[mid] >= x) {
			r = mid - 1;
		}
	}
	if (a[r] == x) {
		return r;
	}
	return -1;
}
int main() {
	int n, m, x, ans[maxn];
	cin >> n >> m;
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	for (int i = 1; i <= m; i++) {
		cin >> x;
		ans[i] = find(1, n, x);
	}
	for (int i = 1; i <= m; i++) {
		cout << ans[i] << endl;
	}
	return 0;
}