public void removeFromStack(char sign){
        ListStack tmp = new ListStack();
        ListStack tmp2 = new ListStack();
        while(!isEmpty()){
            if(getHead().getSign()!=sign)
                tmp.push(pop());
            else pop();
        }
        while(!tmp.isEmpty()){
            tmp2.push(tmp.pop());
        }
        head=tmp2.getHead();
    }