C++ :

#include <bits/stdc++.h>
using namespace std;

int n, m, a[100010], x, t;

int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) 
        cin >> a[i];
    for (int i = 0; i < m; i++) {
    	cin >> x;
    	t = lower_bound(a + 1, a + 1 + n, x) - a;
    	cout << (a[t] == x ? t : -1) << endl;
	}
        
    
    return 0;
}