Consider the sets A1,A2,…,An. Set Ak is composed of k disjoint intervals on the real axis (k=1,2,…,n). Prove that from the intervals contained by these sets, one can choose ⌊2n+1⌋ intervals such that they belong to pairwise different sets Ak, and no two of these intervals have a common point. floor functioncombinatorics unsolvedcombinatorics