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1200: Choosy in Food

Time Limit: 1 Sec Memory Limit: 1280 MB
Submit: 32 Solved: 5
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Description

Xiao Ming find n trees (labeled 0...n-1) which join a circle in a magical land. Each tree
is covered with ripe berries. Xiao Ming wants to find the tree whose berries are most delicious. He starts from the tree X, walks clockwise to find the target. Each time the probability of him walking k trees is Pk% . P1+P2+..+Pk = 100

Now we know the target of Xiao Ming is the tree Y. Require to know expectation of the number of the trees which Xiao Ming walk through

Input

The first parameter is T, indicates the case number.

In each case, there are four integers at the first line, N, M, X , Y (Tree labels from 0 to N-1, N < 100, M < N).

Output

The expectation of the number of trees Xiao Ming walk through. It will be reserved two decimal places. If Xiao Ming will never arrive the tree, output -1.

Sample Input

Sample Output

4.20
2.00

HINT

hzau 1200 Choosy in Food

原文：http://www.cnblogs.com/bofengyu/p/6790489.html