使用lower_bound即可

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e6 + 5;
int n, m, a[MAXN], q;
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    for (int i = 1; i <= n; i++) cin >> a[i];
    sort (a + 1, a + n + 1);
    for (int i = 1, x; i <= m; i++)
    {
        cin >> q, x = lower_bound(a + 1, a + n + 1, q) - a;
        while (a[x] == q) x++;
        cout << ((a[x - 1] == q) ? n - x + 2 : -1) << " ";
    }
    return 0;
}