A=[2,3,5,7,11,13] B=[4,6,8,9,10,12] P,C=gets.split.map(&:to_i) h={1=>1.0} P.times{ x=Hash.new(0) h.each{|k,v|A.each{|e|x[k*e]+=v/6.0}} h=x } C.times{ x=Hash.new(0) h.each{|k,v|B.each{|e|x[k*e]+=v/6.0}} h=x } p h.reduce(0){|s,(k,v)|s+=k*v}