Let p be a prime and let a and b be integers modulo, P. The inversive crongruential generator (ICO) is a sequences (u n) of pssudorandom numbers defined by the relation un+1 =aun-1 + b mod p. We alow that if b and sufficiently many of the ost significant bist of three consercutive values 2/n of the ICC are given, one can recover in polynomial time the initial value uo (even in the case where the confficient a is unkown) provided that the initial valua uo does not lie in certain email subset of exceptional values