[26] Show that there are strings x, y, z such that C(x|y) +

C(x|z) > C(x) + C(x|y, z) + O(1). For convenience prove this first for strings of the same length n; but it also holds for some strings x, y, z with l(x) = log n and l(y) = l(z) = n. Comments. This is a counterintuitive result. Hint: Prove there are pairwise random strings x, y, z such that each string results from ⊕-ing the other two.