#include <bits/stdc++.h>
using namespace std;

template<class T>
struct Point {
	typedef Point P;
	T x, y;
	explicit Point(T x=0, T y=0) : x(x), y(y) {}
	P operator+(P p) const { return P(x+p.x, y+p.y); }
	P operator-(P p) const { return P(x-p.x, y-p.y); }
	P operator*(T d) const { return P(x*d, y*d); }
	P operator/(T d) const { return P(x/d, y/d); }
	T dist2() const { return x*x + y*y; }
	double dist() const { return sqrt((double)dist2()); }
};

typedef Point<long double> P;

vector<pair<P, P>> segments;

template<class F>
long double ternSearch(P a, P b, F f) {
	while((b - a).dist2() > 1e-15) {
		P p1 = (a*2 + b) / 3;
		P p2 = (a + b*2) / 3;
		if (f(p1) > f(p2)) a = p1;
		else b = p2;
	}
	return f(a);
}

long double solve(int lo, int hi, P start, P end) {
    if(lo == hi) return (end - start).dist();

	int mid = (lo + hi) / 2;
	P p1, p2; tie(p1, p2) = segments[mid];
	
	auto eval = [&](P midpoint) {
		return solve(lo, mid, start, midpoint) + solve(mid+1, hi, midpoint, end);
	};
	return ternSearch(p1, p2, eval);
}

int main() {
    int n;
	cin >> n;
	P start, end;
	segments.resize(n);
	cin >> start.x >> start.y;
	for(int i = 0; i < n; i++)
		cin >> segments[i].first.x >> segments[i].first.y >> segments[i].second.x >> segments[i].second.y;
	cin >> end.x >> end.y;

	cout << setprecision(12) << fixed << solve(0, n, start, end) << "\n";
}