Problem:
Network Reliability

An undirected graph is given.
Each edge of the graph disappears with a constant probability.
Calculate the probability with which the remained graph is connected.

Input

The first line contains three integers N (1 \leq N \leq 14), M (0 \leq M \leq 100) and P (0 \leq P \leq 100), separated by a single space.
N is the number of the vertices and M is the number of the edges. P is the probability represented by a percentage.

The following M lines describe the edges.
Each line contains two integers v_i and u_i (1 \leq u_i, v_i \leq N).
(u_i, v_i) indicates the edge that connects the two vertices u_i and v_i.

Output

Output a line containing the probability with which the remained graph is connected.
Your program may output an arbitrary number of digits after the decimal point. However, the absolute error should be 10^{-9} or less.

Sample Input 1

3 3 50
1 2
2 3
3 1

Output for the Sample Input 1

0.500000000000

Sample Input 2

3 3 10
1 2
2 3
3 1

Output for the Sample Input 2

0.972000000000

Sample Input 3

4 5 50
1 2
2 3
3 4
4 1
1 3

Output for the Sample Input 3

0.437500000000

Solution in Ruby (judge verdict: Wrong Answer)

n, m, q = gets.split.map(&:to_i)

prob = {}
(1..m).each do
    i, j = gets.split.map(&:to_i) 
    prob[[i, j]] = q / 100.0
end

def f(n, prob)
    return 1 if n == 1
    return 0 if disconnected?(n, prob)
    i, j = prob.keys[0]

    new_prob = prob.dup
    new_prob.delete([i, j])
    ans = prob[[i, j]] * f(n, new_prob)

    new_prob = Hash.new(1.0)
    prob.each do |key, q|
        u, v = key
        next if key == [i, j]
        u = j if key[0] == i
        v = j if key[1] == i
        new_prob[[u, v].sort] *= prob[key]
    end

    ans += (1.0 - prob[[i,j]]) * f(n-1, new_prob)
end

def disconnected?(n, prob)
    vs = prob.keys.flatten.uniq
    cc = Hash[*vs.zip(vs).flatten]
    return true if cc.size != n
    prob.keys.each do |i, j|
        cc1 = cc[i]
        cc2 = cc[j]
        cc.each do |k, c|
            cc[k] = cc2 if c == cc1
        end
    end
    cc.values.uniq.size > 1
end

p f(n, prob)