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

    v = 0
    M = N
    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

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

    ans = v(j) - 1 + 9*(j-1)
    do i = 1,j-1
    if(v(i) < 9) then
    exit
    else if(i == j-1)then
    ans = ans + 1
    end if
    end do
    write(*,*) ans      

    stop
end program