program next_alphabet
    implicit none
    character(1):: c
    character(26), parameter:: alphabet = "abcdefghijklmnopqrstuvwxyz"
    integer:: i

    read*, c
    do i=1, 26
        if (alphabet(i:i) == c)then
            print*, alphabet(i+1:i+1)
            stop
        end if
    end do
end program next_alphabet