IMO 1982 LL BRA12

Let there be 3399 numbers arbitrarily chosen among the first

imolonglistmathematicsolympiad

IMO 1982 LL BRA12

Origin: BRA

Problem

Let there be 3399 numbers arbitrarily chosen among the first 6798 integers 1, 2, . . ., 6798 in such a way that none of them divides an- other. Prove that there are exactly 1982 numbers in {1, 2, . . ., 6798} that must end up being chosen.