Save Luke



Save Luke

Crawling in process...Crawling failedTime Limit:1000MS    Memory Limit:262144KB     64bit IO Format:%I64d & %I64u

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Description

Luke Skywalker got locked up in a rubbish shredder between two presses. R2D2 is already working on his rescue, but Luke needs to stay alive as long as possible. For simplicity we will assume that everything happens on a straight line, the presses are initially at coordinates 0 andL, and they move towards each other with speedv₁ and v₂, respectively. Luke has width d and is able to choose any position between the presses. Luke dies as soon as the distance between the presses is less than his width. Your task is to determine for how long Luke can stay alive.

Input

The first line of the input contains four integersd, L,v₁, v₂ (1 ≤ d, L, v₁, v₂ ≤ 10 000, d < L) — Luke's width, the initial position of the second press and the speed of the first and second presses, respectively.

Output

Print a single real value — the maximum period of time Luke can stay alive for. Your answer will be considered correct if its absolute or relative error does not exceed10^- 6.

Namely: let's assume that your answer is a, and the answer of the jury is b. The checker program will consider your answer correct, if.

Sample Input

Input

2 6 2 2

Output

1.00000000000000000000

Input

1 9 1 2

Output

2.66666666666666650000

Sample Output

Hint

In the first sample Luke should stay exactly in the middle of the segment, that is at coordinates[2;4], as the presses move with the same speed.

In the second sample he needs to occupy the position. In this case both presses move to his edges at the same time.

题目大意：一个人在一条路上，给出这个人的身宽，路的两端有俩碾压机，向中间靠拢着行驶，给了路的长度，给了俩碾压机的速度，求这个人最多能存活多久。

解题思路：相对运动。。。（PS：注意精度）

代码如下：

#include<stdio.h> int main(){double d,l,v1,v2;scanf("%lf%lf%lf%lf",&d,&l,&v1,&v2);printf("%.20lf\n",(l-d)/(v1+v2));return 0;}