输入描述:

The input consists of multiple datasets. Each dataset represents a map of an island, which is a
convex polygon. The format of a dataset is as follows.

 
.
.
.
 
Every input item in a dataset is a non-negative integer. Two input items in a line are separated
by a space.
 in the first line is the number of vertices of the polygon, satisfying . Subsequent  lines are the x- and y-coordinates of the n vertices. Line segments 
() and the line segment ()–() form the border of the polygon in counterclockwise order. That is, these line segments see the inside of the polygon in the left of
their directions. All coordinate values are between 0 and 10000, inclusive.
You can assume that the polygon is simple, that is, its border never crosses or touches itself. As
stated above, the given polygon is always a convex one.
The last dataset is followed by a line containing a single zero.

输出描述:

For each dataset in the input, one line containing the distance of the most distant point from
the sea should be output. An output line should not contain extra characters such as spaces.

The answer should not have an error greater than 0.00001 (10−5). You may output any number
of digits after the decimal point, provided that the above accuracy condition is satisfied.

4
0 0
10000 0
10000 10000
0 10000
3
0 0
10000 0
7000 1000
6
0 40
100 20
250 40
250 70
100 90
0 70
3
0 0
10000 10000
5000 5001
0

5000.000000
494.233641
34.542948
0.353553

备注:

ACM International Collegiate Programming Contest, Asia Regional 2007, Japan
POJ 3608