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## J. Martian Farmlands

Time limit: 1.0 second
Memory limit: 64 MB
Alexey Ivanovich decided to sell his farmland on Mars and return to his dear Venus. His farmland has the shape of a flat rectangular triangle ABC, which contains a narrow straight irrigation channel AF. Unfortunately, Alexey Ivanovich didn’t manage to find a buyer quickly. It turned out that cottagers wanted to buy only farmlands with through irrigation channel, i.e., a channel having exactly two common points with a border line of a farmland.
Alexey Ivanovich realized that he could divide his farmland into several smaller ones and sell them separately. He decided to divide the initial farmland into two identical triangular farmlands of the same shape by drawing an altitude to the hypotenuse. Then he would consider the half containing F inside and do the same—draw another altitude to the hypotenuse and consider the smaller farmland containing point F. The process would go on until point F is on another altitude, or until the size of the new farmlands is negligibly small.
Help Alexey Ivanovich to count the total area of all resulting farmlands which he will be able to sell.

### Input

Let’s introduce the coordinates in such a way that point A has the coordinates (0, 0), point B has the coordinates (10, 0) and point C has coordinates (10, 10). The only line contains real numbers x and y that are coordinates of point F (0 < y < x < 10). Numbers x and y are specified with at most three digits after decimal point.

### Output

Output the total area of the farmlands fit for sale with absolute or relative error of at most 10−3.

### Sample

inputoutput
```8.125 4.375
```
```29.6875
```
Problem Author: Andrey Demidov
Problem Source: Open Ural FU Personal Contest 2012
To submit the solution for this problem go to the Problem set: 1950. Martian Farmlands