Andrew recently bought a special car, which has ** two** engines. He can use both engines of the car or only one of the two engines.

If he uses only the first engine, the car would move at the speed ** v_{1}**.

If he uses only the second engine, the car would move at the speed

**.**

`v`_{2}But if the car uses both engines, it would move at speed

**.**

`v = v`_{1}+ v_{2} He wants to travel from **Iasi** to **Cluj-Napoca** to reach the final round of **MindCoding**. For this purpose, he did some benchmarks and found that if he uses only the first engine, he would traverse the distance between the two cities in ** t_{1}** minutes (you may consider that the car moves with a constant velocity

**) and if he uses only the second engine, the car would traverse this distance in**

`v`_{1}**minutes (you may consider that the car moves with a constant velocity**

`t`_{2}**). Because none of these times are small enough to arrive before the start of the contest in**

`v`_{2}**, Andrew decided to use both engines.**

`Cluj-Napoca` But just before leaving, a friend specialized in mechanics helped him to improve his engine power. He increased the power of the first engine ** k_{1}** times and the power of the second one

**times. Thus, the new speed of the first engine will be**

`k`_{2}**, and the second one's speed will be**

`v`_{1}*k_{1}**. Now with both engines he can travel the distance from**

`v`_{2}*k_{2}**to**

`Iasi`**with speed**

`Cluj-Napoca`**, but he doesn't know how to compute the**

`v`_{1}*k_{1}+ v_{2}*k_{2}**needed for him to arrive at the destination.**

`time` Your task is to compute that time, knowing only ** t_{1}**,

**and**

`t`_{2}**,**

`k`_{1}**.**

`k`_{2}### Input

The first line of input contains four integers ** t_{1}, k_{1}, t_{2}, k_{2}**, in this order, separated by spaces.

### Output

The only line of output should contain the needed time to arrive at the destination, travelling with speed ** v_{1}*k_{1} + v_{2}*k_{2}**.

### Restrictions

`1 ≤ v`_{1}, v_{2}, k_{1}, k_{2}≤ 100`Your result is tested agains ours. Your output will be correct if the absolute value between our answer and your answer is ≤ 0.0001`

### Sample

Input | Output |
---|---|

5 5 20 20 | 0.5 |