  We prove that for any finite set A of real numbers its difference set D:=A-A
has large product set and quotient set, namely, |DD|, |D/D| \gg |D|^{1+c},
where c>0 is an absolute constant. A similar result takes place in the prime
field F_p for sufficiently small D. It gives, in particular, that
multiplicative subgroups of size less than p^{4/5-\eps} cannot be represented
in the form A-A for any A from F_p.
