program prob4
    implicit none
    integer(16)::N, M
    integer(16)::i,j,ans,com
    integer::v(17)
    read(*,*) N

    v = 0

    if(N < 10) then
        write(*,*) N
    else
        N = N + 1
        do i = 16, 0, -1
            if(N >= 10**i) then
                v(i+1) = N/(10**i)
                N = N - N/(10**i) * 10**i
            end if
        end do

        do i = 17, 1, -1
            if(v(i) > 0)then
                j = i
                exit
            end if
        end do

        ans = v(j) - 1 + 9*(j-1)
        write(*,*) ans      
    end if

    stop
end program