Algo(X,T,P,Cnt)
IF CNT=-1 THEN
    RETURN cnt
IF t!=nil THEN
        cnt=algo(x,t->sx,t,cnt)
        IF cnt!=-1
        IF cnt<x THEN
                cnt=cnt+1
        ELSE
            cancella(T,P)
            cnt=-1
        cnt=algo(x,T->dx,T,cnt)
RETURN CNT