下面C++程序的运行结果为（ ）。

#include <iostream>
int query(int n, int *a, int x) {
    int l = 0, r = n;
    while (l < r) {
        int mid = l + (r - l) / 2;
        if (a[mid] >= x) r = mid;
        else l = mid + 1;
    }
    if (l == n) return -1;
    return l;
}
int main() {
    int n = 10;
    int x = 3;
    int num[] = {1, 2, 2, 3, 3, 4, 5, 5, 6, 7};
    std::cout << query(n, num, x) << "\n";
    return 0;
}