nr of rect with lines ll with Ox, Oy

#include <bits/stdc++.h>
#define x first
#define y second
using namespace std;
using Point = pair<int, int>;

istream &operator >> (istream &in, Point &point) {
    in >> point.x >> point.y;
    return in;
}

int solve(const set<Point> &points) {
    int ans = 0;
    set<Point>::const_iterator it1, it2;
    for (it1 = cbegin(points); it1 != cend(points); it1++) {
        it2 = it1;
        advance(it2, 1);
        for (; it2 != cend(points); it2++) {
            if (it1->x == it2->x || it1->y == it2->y) {
                continue;
            }

            const auto &p3 = Point(it1->x, it2->y);
            const auto &p4 = Point(it2->x, it1->y);

            if (points.count(p3) && points.count(p4)) {
                ans++;
            }
        }
    }
    return ans >> 1;
}

signed main() {
    int n;
    cin >> n;
    vector<Point> points(n);
    for (auto &point : points) {
        cin >> point;
    }//*/
    cout << "Nr. of rectangles with lines || with Ox, Oy is: ";
    cout << solve(set<Point>(cbegin(points), cend(points))) << endl;
    return 0;
}