;513.asm

        .model small
        .data
max     db 100
act     db ?
string  db 100 dup(?)
        .stack 100h
        .code
main    proc  far
start:  mov   ax,@data
        mov   ds,ax
        lea   dx,max
        mov   ah,0ah
        int   21h
        mov   si,0
        mov   ch,act
loop1:  cmp   string[si],30h
        jl    next
        cmp   string[si],39h
        jg    next
        or    cl,10h
        jmp   short  exit
next:   inc   si
        dec   ch
        jnz   loop1
        and   cl,0efh
exit:   mov   ax,4c00h
        int   21h
main    endp
        end   start