.global main
.text


main:
    loop:
        ldr r0, =stdin
        ldr r0, [r0]        //get pointer to istream
        push {lr}           //to get lr
        bl fgetc            //get char to r0 from stdin, fgetc can't guarantee safety of lr
        pop {lr}            //save lr
        cmp r0, #-1         //-1 means stdin finish
        bxeq lr
        cmp r0, #57         //ASCII code of '0' is 47
        cmpls r0, #46       //ASCII code of '9' is 57, compare if prev correct
        ldrgt r1, =stdout   //print if prev correct(will implemented if prevprev correct)
        ldrgt r1, [r1]      //r1 is ostream pointer
        pushgt {lr}         //to get lr
        blgt fputc          //print char to ostream if condition OK
        popgt {lr}          //save rl
        b loop              //go to loop label (implementation of loop)