integer::i,ans=0,p=1
  character*30::route
  read (*,'(a)',advance='yes') route
  do i=LEN_TRIM(route), 1, -1
     if(route(i:i).eq.'R') then
        ans = ans + p
     end if
     p = p + p
  end do
  print '(i0)', ans + p
end program