struct tnode * dodaj_na_koniec (struct tnode *beg, int val){
        struct tnode * nowy= malloc (sizeof (struct tnode));
        struct tnode *p;
        nowy->value=val;
        nowy->next=NULL;
        if(beg==NULL) beg=nowy;
        else{
                p=beg;
                while(p->next)
                        p=p->next;
                p->next=nowy;
        }
        return beg;
}