AlgoIT(T,a,b)
    ct=-1 st=null
    next=last=null
    ret=null
    while(ct!=null && st!=null) then
        if(ct!=null) then
            if(ct->key<b) then
                st=push(ct,st)
                next=ct->dx
            else
                st=push(st)
                next=ct->sx
        else
            ct=top(st)
            if(ct->dx!=null && ct->dx!=last) then
                ct->sx=ret
                if(ct->key<a) then
                    ret=ct
                else
                    next=ct->dx
            else
                if(ct->dx!=null) then
                    if(ct->key>b) then
                        ct->dx=ret
                        ret=ct
                    else
                        ct->dx=ret
                        ct=F(ct)
                        ret=ct
                else
                    if(ct->key>b) then
                        ct->dx=null
                        ret=ct
                        next=null
                    else
                        ct->dx=null
                        ct=F(ct)
                        ret=ct
                    st=pop(st)

        last=ct
        ct=next

    return ret