character*10::A,B
  character::numa,numb
  integer::lena,lenb,i
  read  *,A,B
  lena = LEN_TRIM(A)
  lenb = LEN_TRIM(B)
  if(lena.gt.lenb) then
     print '(a)', TRIM(A)
  else if(lenb.gt.lena) then
     print '(a)', TRIM(B)
  else
     do i=1,lena
        numa = A(i:i)
        numb = B(i:i)
        if(numa.eq.numb) cycle
        if(numa.eq.'7' .and. numb.eq.'4') then
           print '(a)', TRIM(B)
           exit
        else if(numa.eq.'4' .and. numb.eq.'7') then
           print '(a)', TRIM(A)
           exit
        else if(numa.gt.numb) then
           print '(a)', TRIM(A)
           exit
        else
           print '(a)', TRIM(B)
           exit
        end if
     end do
  end if
end program