2327: Choosy in Food

    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

    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).  

     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. 

2 
4 2 0 1
50 50 
4 1 0 2 
100

4.20
2.00