获得大于等于x的第一个数

5 3
6 3 8 5 9
7
3
10

8
5
-1

#include <iostream>
#include <set>
#include <algorithm>

int main() {
    int n, m;
    std::cin >> n >> m;

    std::set<int> a;
    for (int i = 0; i < n; i++) {
        int num;
        std::cin >> num;
        a.insert(num);
    }

    for (int i = 0; i < m; i++) {
        int x;
        std::cin >> x;

        // Find the smallest number in the set greater than x
        auto it = std::upper_bound(a.begin(), a.end(), x);

        if (it != a.end()) {
            std::cout << *it << std::endl;
        } else {
            std::cout << -1 << std::endl;
        }
    }

    return 0;
}