#include <stdio.h>
#include <math.h>

#include <algorithm>
#include <utility>

using namespace std;

const double EPS = 1e-10;
#define MAX 1000

int cmp(double x, double y = 0, double tol = EPS) {
	  return (x <= y + tol) ? (x + tol < y) ? -1 : 0 : 1;
}

struct point {
	double x, y;
	point(double x = 0, double y = 0): x(x), y(y) {}
	point operator +(point q) { return point(x + q.x, y + q.y); }
	point operator -(point q) { return point(x - q.x, y - q.y); }
	point operator *(double t) { return point(x * t, y * t); }
	point operator /(double t) { return point(x / t, y / t); }
	double operator *(point q) { return x * q.x + y * q.y; }
	double operator %(point q) { return x * q.y - y * q.x; }
	int cmp(point q) const {
		if (int t = ::cmp(x, q.x)) return t;
		return ::cmp(y, q.y);
	}
	bool operator ==(point q) const { return cmp(q) == 0; }
	bool operator !=(point q) const { return cmp(q) != 0; }
	bool operator < (point q) const { return cmp(q) <  0; }

};

double seg_distance(point p, point q, point r) {
	point A = r - q, B = r - p, C = q - p;
	double a = A * A, b = B * B, c = C * C;
	if (cmp(b, a + c) >= 0) return sqrt(a);
	else if (cmp(a, b + c) >= 0) return sqrt(b);
	else return fabs(A % B) / sqrt(c);
}

double segs_distance(point p, point q, point r, point s) {
	return min(min(seg_distance(p, q, r),
			       seg_distance(p, q, s)),
			   min(seg_distance(r, s, p),
				   seg_distance(r, s, q)));
}

double abs(point p) { return hypot(p.x, p.y); }
double arg(point p) { return atan2(p.y, p.x); }

int N;
double L, H;
point Pi[MAX], Pf[MAX];

int main() {
	int k;
	double ans;
	while (scanf(" %d", &N) != EOF) {
		ans = 1e10;
		scanf(" %lf %lf", &L, &H);
		for (k = 0; k < N; k++) {
			Pi[k].x = (k % 2 == 0) ? 0.0 : L;
			scanf(" %lf %lf %lf", &Pi[k].y, &Pf[k].x, &Pf[k].y);
		}
		for (k = 0; k < N; k++) {
			if (k % 2 == 0) {
				ans = min(ans, segs_distance(point(L, 0), point(L, H), Pi[k], Pf[k]));
			} else {
				ans = min(ans, segs_distance(point(0, 0), point(0, H), Pi[k], Pf[k]));
			}
			if (k > 0) {
				ans = min(ans, segs_distance(Pi[k], Pf[k], Pi[k-1], Pf[k-1]));
			}
		}
		printf("%.2f\n", ans);
	}
}