@pz,@q = gets.split.map{|e|e.to_f/100.0}

@memo={}
def calc(pi,deep)
    pi = pi<0 ? 0.0 : 1<pi ? 1.0 : pi
    
    key = [pi,deep]                  # <---bugfix!!
    
    return @memo[key] if @memo[key]
    return 1.0 if deep>200
    
    r = 0.0
    #used
    r += (1.0 + calc(pi-@q,deep+1)) /2.0 * (pi)     if pi >0.0
    #unused
    r += (1.0 + calc(pi+@q,deep+1)) /3.0 * (1.0-pi) if pi <1.0
    
    return @memo[key] = r
end

result = (1.0 + calc(@pz,0)) / 3.0 

p result.to_f