program main
  integer::N
  integer::A(4),B(4)
  integer::AA(4,24),BB(4,24)
  integer::AAA(24)
  integer::i,j,k,l,indx = 0,total=0,pat=1

  read *,N
  read *,A(1:N), B(1:N)
  do i=1,N
     if(N.eq.1) then
        indx = indx + 1
        AA(1,indx) = A(i)
        BB(1,indx) = B(i)
        cycle
     end if
     do j=1,N
        if(i.eq.j) cycle
        if(N.eq.2) then
           indx = indx + 1
           AA(1:2,indx) = (/A(i),A(j)/)
           BB(1:2,indx) = (/B(i),B(j)/)
           cycle
        end if
        do k=1,N
           if(i.eq.k) cycle
           if(j.eq.k) cycle
           if(N.eq.3) then
              indx = indx + 1
              AA(1:3,indx) = (/A(i),A(j),A(k)/)
              BB(1:3,indx) = (/B(i),B(j),B(k)/)
              cycle
           end if
           do l=1,N
              if(i.eq.l) cycle
              if(j.eq.l) cycle
              if(k.eq.l) cycle
              indx = indx + 1
              AA(1:4,indx) = (/A(i),A(j),A(k),A(l)/)
              BB(1:4,indx) = (/B(i),B(j),B(k),B(l)/)
           end do
        end do
     end do
  end do

  do i=2,N
     pat=pat*i
  end do

  do i=1,pat
     do j=1,pat
        AAA(j) = 0
        do k=1,N
           if ( AA(k,i).gt.BB(k,j) ) then
              AAA(j) = AAA(j) + 1
           else if ( AA(k,i).lt.BB(k,j) ) then
              AAA(j) = AAA(j) - 1
           end if
        end do
     end do
     total = total + COUNT(AAA(1:pat).gt.0)
  end do

  print '(a,f0.2)', '0',REAL(total)/REAL(pat*pat)

end program main