sweep line

int n;
cin >> n;
 
vector<array<int, 4>> ls;
 
for (int i = 0; i < n; i++) {
    int x1, y1, x2, y2;
 
    cin >> x1 >> y1 >> x2 >> y2;
    x1 += 1e6; x2 += 1e6;
 
    if (y1 == y2) {
        ls.push_back({y1, 2, x1, x2});
    } else {
        ls.push_back({y1, 0, x1, x1});
        ls.push_back({y2, 1, x2, x2});
    }
}
sort(begin(ls), end(ls));
 
BIT bit(2 * 1e6 + 1);
long long ans;
for (auto [y, ty, x1, x2] : ls) {
    if (ty == 0) {
        bit.add(x1, 1);
    } else if (ty == 1) {
        bit.add(x1, -1);
    } else {
        ans += bit.range(x1, x2);
    }
}