If n + 1 integers are chosen from the set {1, 2, 3,..., 2n), where n is a positive integer, must at least one of them be even? To answer this question, let S = {1, 2, 3, ..., 2n}, where n is a positive integer, and note that in S there are exactly for at least one of the elements of T to be even. Thus, the answer to this question is Yes number of odd integers in T, it is necessary odd integers. Since n+1 is greater than the