require'timeout'
k=gets.to_i
ss=0
c=0
begin
timeout(2){
  loop{
    s=0
    i=0
    while s!=k
      i+=1
      s=0 if s>k
      s+=[*1..6].sample
    end
    c+=1
    ss+=i
  }
}
rescue Timeout::Error
end
p 1.0*ss/c