Problem: It's a beautiful April day and Wallace is playing football with his friends. But his friends do not know that Wallace actually stayed home with Gromit and sent them his robotic self instead. Robo-Wallace has several advantages over the other guys. For example, he can hit the ball directly to the specified point. And yet, the notion of a giveaway is foreign to him. The combination of these features makes the Robo-Wallace the perfect footballer — as soon as the ball gets to him, he can just aim and hit the goal. He followed this tactics in the first half of the match, but he hit the goal rarely. The opposing team has a very good goalkeeper who catches most of the balls that fly directly into the goal. But Robo-Wallace is a quick thinker, he realized that he can cheat the goalkeeper. After all, they are playing in a football box with solid walls. Robo-Wallace can kick the ball to the other side, then the goalkeeper will not try to catch the ball. Then, if the ball bounces off the wall and flies into the goal, the goal will at last be scored.

Your task is to help Robo-Wallace to detect a spot on the wall of the football box, to which the robot should kick the ball, so that the ball bounces once and only once off this wall and goes straight to the goal. In the first half of the match Robo-Wallace got a ball in the head and was severely hit. As a result, some of the schemes have been damaged. Because of the damage, Robo-Wallace can only aim to his right wall (Robo-Wallace is standing with his face to the opposing team's goal).

The football box is rectangular. Let's introduce a two-dimensional coordinate system so that point (0, 0) lies in the lower left corner of the field, if you look at the box above. Robo-Wallace is playing for the team, whose goal is to the right. It is an improvised football field, so the gate of Robo-Wallace's rivals may be not in the middle of the left wall.

<image>

In the given coordinate system you are given: 

  * y1, y2 — the y-coordinates of the side pillars of the goalposts of robo-Wallace's opponents; 
  * yw — the y-coordinate of the wall to which Robo-Wallace is aiming; 
  * xb, yb — the coordinates of the ball's position when it is hit; 
  * r — the radius of the ball. 



A goal is scored when the center of the ball crosses the OY axis in the given coordinate system between (0, y1) and (0, y2). The ball moves along a straight line. The ball's hit on the wall is perfectly elastic (the ball does not shrink from the hit), the angle of incidence equals the angle of reflection. If the ball bounces off the wall not to the goal, that is, if it hits the other wall or the goal post, then the opposing team catches the ball and Robo-Wallace starts looking for miscalculation and gets dysfunctional. Such an outcome, if possible, should be avoided. We assume that the ball touches an object, if the distance from the center of the ball to the object is no greater than the ball radius r.

Input

The first and the single line contains integers y1, y2, yw, xb, yb, r (1 ≤ y1, y2, yw, xb, yb ≤ 106; y1 < y2 < yw; yb + r < yw; 2·r < y2 - y1).

It is guaranteed that the ball is positioned correctly in the field, doesn't cross any wall, doesn't touch the wall that Robo-Wallace is aiming at. The goal posts can't be located in the field corners.

Output

If Robo-Wallace can't score a goal in the described manner, print "-1" (without the quotes). Otherwise, print a single number xw — the abscissa of his point of aiming. 

If there are multiple points of aiming, print the abscissa of any of them. When checking the correctness of the answer, all comparisons are made with the permissible absolute error, equal to 10 - 8. 

It is recommended to print as many characters after the decimal point as possible.

Examples

Input

4 10 13 10 3 1


Output

4.3750000000


Input

1 4 6 2 2 1


Output

-1


Input

3 10 15 17 9 2


Output

11.3333333333

Note

Note that in the first and third samples other correct values of abscissa xw are also possible.

Solution (in JAVA):

Solution:
/* Codeforces Template */

import java.io.*;
import java.util.*;

import static java.lang.Math.*;
import static java.util.Arrays.fill;
import static java.util.Arrays.binarySearch;
import static java.util.Arrays.sort;

public class Main {
	
	static long initTime;
	static final Random rnd = new Random(7777L);
	static boolean writeLog = false;
	
	public static void main(String[] args) throws IOException {
		initTime = System.currentTimeMillis();
		try {
			writeLog = "true".equals(System.getProperty("LOCAL_RUN_7777"));
		} catch (SecurityException e) {}
		new Thread(null, new Runnable() {
			public void run() {
				try {
					try {
						if (new File("input.txt").exists())
							System.setIn(new FileInputStream("input.txt"));
					} catch (SecurityException e) {}
					long prevTime = System.currentTimeMillis();
					new Main().run();
					log("Total time: " + (System.currentTimeMillis() - prevTime) + " ms");
					log("Memory status: " + memoryStatus());
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}, "1", 1L << 24).start(); 
	}

	void run() throws IOException {
		in = new BufferedReader(new InputStreamReader(System.in));
		out = new PrintWriter(System.out);
		solve();
		out.close();
		in.close();
	}
	
	/*************************************************************** 
	 * Solution
	 **************************************************************/

	final double EPS = 1e-8;
	double r;
	
	void solve() throws IOException  {
		
		double y1 = nextDouble();
		double y2 = nextDouble();
		double yw = nextDouble();
		double xb = nextDouble();
		double yb = nextDouble();
		
		r = nextDouble();

		double h = yw - r;
		
		double ry1 = h + h - y1;
		double ry2 = h + h - y2;
		
		double ay = min(h + h, ry1 - r);

		Point2D aim = new Point2D(0.0, ay);
		
		Line2D trace = new Line2D(new Point2D(xb, yb), aim);

		Point2D rp2 = new Point2D(0.0, ry2);
		
		if (bad(trace, rp2)) {
			out.println(-1);
			return;
		}
		
		Line2D ceil = new Line2D(new Point2D(-1.0, h), new Point2D(1e6, h));
		out.printf(Locale.US, "%.12f%n", cll(trace, ceil).x);
	}
	
	boolean bad(Line2D trace, Point2D p) {
		return dsp(trace, p) < r - 1e-9;
	}

	double dsp(Line2D l, Point2D p) {
		return l.dist(p);
	}

	Point2D cll(Line2D l1, Line2D l2) {
		double det = -det2x2(l1.A, l1.B, l2.A, l2.B);
//		if (abs(det) < EPS) return null;
		return new Point2D(det2x2(l1.C, l1.B, l2.C, l2.B) / det, det2x2(l1.A, l1.C, l2.A, l2.C) / det);
	}
	double sqr(double x) { return x * x; }
	double det2x2(double a11, double a12, double a21, double a22) { return a11 * a22 - a12 * a21; }
	double cross(Point2D p0, Point2D p1, Point2D p2) { return (p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y); }
	double distSqr(Point2D p1, Point2D p2) { return sqr(p2.x - p1.x) + sqr(p2.y - p1.y); }
	double dist(Point2D p1, Point2D p2) { return sqrt(distSqr(p1, p2)); }
	double area(Point2D p1, Point2D p2, Point2D p3) { return 0.5 * abs(cross(p1, p2, p3)); }
	double area(Point2D[] p) {
		if (p.length < 3) return 0.0;
		double ret = 0.0;
		for (int i = 0, j = 1; i < p.length; i++, j = (++j == p.length ? 0 : j))
			ret += p[i].crossProduct(p[j]);
		return 0.5 * ret;
	}
	class Point2D {
		double x, y, d, a;
		Point2D() { x = y = 0.0; }
		Point2D(double x, double y) { this.set(x, y); }
		Point2D set(double x, double y) { this.x = x; this.y = y; return this; }
		Point2D copy() { return new Point2D(x, y); }
		Point2D add(Point2D v) { return new Point2D(x + v.x, y + v.y); }
		Point2D inc(Point2D v) { return set(x + v.x, y + v.y); }
		Point2D sub(Point2D v) { return new Point2D(x - v.x, y - v.y); }
		Point2D dec(Point2D v) { return set(x - v.x, y - v.y); }
		Point2D mul(double K) { return new Point2D(K * x, K * y); }
		Point2D scale(double K) { return set(K * x, K * y); }
		double len() { return sqrt(x * x + y * y); }
		Point2D norm() { return norm(1.0); }
		Point2D norm(double newLen) { return this.mul(newLen / len()); }
		Point2D normalize() { return this.normalize(1.0); }
		Point2D normalize(double newLen) { return scale(newLen / len()); }
		double scalarProduct(Point2D v) { return x * v.x + y * v.y; }
		double crossProduct(Point2D v) { return x * v.y - v.x * y; }
		Point2D rotate90() { return new Point2D(-y, x); }
		Point2D rotate(double angle) { double cos = cos(angle); double sin = sin(angle); return rotate(cos, sin); }
		Point2D rotate(double cos, double sin) { return new Point2D(x * cos - y * sin, x * sin + y * cos); }
		Point2D turn90() { return set(-y, x); }
		Point2D turn(double angle) { double cos = cos(angle); double sin = sin(angle); return turn(cos, sin); }
		Point2D turn(double cos, double sin) { return set(x * cos - y * sin, x * sin + y * cos); }
	}
	class Line2D {
		Point2D p1, p2;
		double A, B, C;
		Line2D(Point2D p1, Point2D p2) { this.set(p1.copy(), p2.copy()); }
		Line2D(Point2D p, Line2D l) { this.set(p.copy(), l); }
		Line2D(double r, Line2D l) { this.set(r, l); }
		Line2D set(Point2D p1, Point2D p2) {
			this.p1 = p1; this.p2 = p2;
			A = p2.y - p1.y; B = p1.x - p2.x;
			C = -(A * p1.x + B * p1.y);
			return this;
		}
		Line2D set(Point2D p, Line2D l) { // perpendicular
			p1 = p; p2 = p.add(l.normal());
			A = -l.B; B = l.A;
			C = -(A * p1.x + B * p1.y);
			return this;
		}
		Line2D set(double r, Line2D l) { // parallel
			Point2D v = l.normal().normalize(r);
			p1 = l.p1.sub(v); p2 = l.p2.sub(v);
			A = l.A; B = l.B;
			C = -(A * p1.x + B * p1.y);
			return this;
		}
		Line2D move(Point2D v) {
			p1.inc(v); p2.inc(v);
			C = -(A * p1.x + B * p1.y);
			return this;
		}
		Line2D shift(double r) { // move along normal
			Point2D v = this.normal().normalize(r);
			p1.dec(v); p2.dec(v);
			C = -(A * p1.x + B * p1.y);
			return this;
		}
		double calc(Point2D p) { return A * p.x + B * p.y + C; }
		boolean lay(Point2D p) { return abs(this.calc(p)) < EPS; }
		boolean contains(Point2D p) {
			if (!lay(p)) return false; double t = this.getT(p);
			return -EPS < t && t < 1.0 + EPS;
		}
		boolean containsInBB(Point2D p) {
			double minX = min(p1.x, p2.x);
			double maxX = max(p1.x, p2.x);
			double minY = min(p1.y, p2.y);
			double maxY = max(p1.y, p2.y);
			return minX - EPS < p.x && p.x < maxX + EPS && minY - EPS < p.y && p.y < maxY + EPS;
		}
		double getT(Point2D p) {
			if (!this.lay(p)) return Double.NaN;
			if (abs(A) > EPS) return (p.y - p1.y) / A;
			if (abs(B) > EPS) return (p1.x - p.x) / B;
			throw new RuntimeException("Bad line");
		}
		Point2D getPoint(double t) { return new Point2D(p1.x - B * t, p1.y + A * t); }
		double dist(Point2D p) { return abs(this.calc(p)) / sqrt(A * A + B * B); }
		Point2D dir() { return new Point2D(-B, A); }
		Point2D normal() { return new Point2D(A, B); }
		Point2D projection(Point2D p) {
			double t = (B * (p1.x - p.x) - A * (p1.y - p.y)) / (A * A + B * B);
			return new Point2D(p1.x - B * t, p1.y + A * t);
		}
		Line2D projection(Line2D l) { return new Line2D(this.projection(l.p1), this.projection(l.p2)); }
	}
	
	/*************************************************************** 
	 * Input 
	 **************************************************************/
	BufferedReader in;
	PrintWriter out;
	StringTokenizer st = new StringTokenizer("");
	
	String nextToken() throws IOException {
		while (!st.hasMoreTokens())
			st = new StringTokenizer(in.readLine());
		return st.nextToken();
	}
	
	int nextInt() throws IOException {
		return Integer.parseInt(nextToken());
	}
	
	long nextLong() throws IOException {
		return Long.parseLong(nextToken());
	}
	
	double nextDouble() throws IOException {
		return Double.parseDouble(nextToken());
	}
	
	int[] nextIntArray(int size) throws IOException {
		int[] ret = new int [size];
		for (int i = 0; i < size; i++)
			ret[i] = nextInt();
		return ret;
	}
	
	long[] nextLongArray(int size) throws IOException {
		long[] ret = new long [size];
		for (int i = 0; i < size; i++)
			ret[i] = nextLong();
		return ret;
	}
	
	double[] nextDoubleArray(int size) throws IOException {
		double[] ret = new double [size];
		for (int i = 0; i < size; i++)
			ret[i] = nextDouble();
		return ret;
	}
	
	String nextLine() throws IOException {
		st = new StringTokenizer("");
		return in.readLine();
	}
	
	boolean EOF() throws IOException {
		while (!st.hasMoreTokens()) {
			String s = in.readLine();
			if (s == null)
				return true;
			st = new StringTokenizer(s);
		}
		return false;
	}
	
	/*************************************************************** 
	 * Output 
	 **************************************************************/
	void printRepeat(String s, int count) {
		for (int i = 0; i < count; i++)
			out.print(s);
	}
	
	void printArray(int[] array) {
		if (array == null || array.length == 0)
			return;
		for (int i = 0; i < array.length; i++) {
			if (i > 0) out.print(' ');
			out.print(array[i]);
		}
		out.println();
	}
	
	void printArray(long[] array) {
		if (array == null || array.length == 0)
			return;
		for (int i = 0; i < array.length; i++) {
			if (i > 0) out.print(' ');
			out.print(array[i]);
		}
		out.println();
	}
	
	void printArray(double[] array) {
		if (array == null || array.length == 0)
			return;
		for (int i = 0; i < array.length; i++) {
			if (i > 0) out.print(' ');
			out.print(array[i]);
		}
		out.println();
	}
	
	void printArray(double[] array, String spec) {
		if (array == null || array.length == 0)
			return;
		for (int i = 0; i < array.length; i++) {
			if (i > 0) out.print(' ');
			out.printf(Locale.US, spec, array[i]);
		}
		out.println();
	}
	
	void printArray(Object[] array) {
		if (array == null || array.length == 0)
			return;
		boolean blank = false;
		for (Object x : array) {
			if (blank) out.print(' '); else blank = true;
			out.print(x);
		}
		out.println();
	}
	
	@SuppressWarnings("rawtypes")
	void printCollection(Collection collection) {
		if (collection == null || collection.isEmpty())
			return;
		boolean blank = false;
		for (Object x : collection) {
			if (blank) out.print(' '); else blank = true;
			out.print(x);
		}
		out.println();
	}
	
	/*************************************************************** 
	 * Utility
	 **************************************************************/
	static String memoryStatus() {
		return (Runtime.getRuntime().totalMemory() - Runtime.getRuntime().freeMemory() >> 20) + "/" + (Runtime.getRuntime().totalMemory() >> 20) + " MB";
	}
	
	static void checkMemory() {
		System.err.println(memoryStatus());
	}
	
	static long prevTimeStamp = Long.MIN_VALUE;
	
	static void updateTimer() {
		prevTimeStamp = System.currentTimeMillis();
	}
	
	static long elapsedTime() {
		return (System.currentTimeMillis() - prevTimeStamp);
	}
	
	static void checkTimer() {
		System.err.println(elapsedTime() + " ms");
	}
	
	static void chk(boolean f) {
		if (!f) throw new RuntimeException("Assert failed");
	}
	
	static void chk(boolean f, String format, Object ... args) {
		if (!f) throw new RuntimeException(String.format(format, args));
	}
	
	static void log(String format, Object ... args) {
		if (writeLog) System.err.println(String.format(Locale.US, format, args));
	}
}