TOT 405 1994 Spring A J3 450 members of a parliament give a slap
Source:
June 12, 2024
combinatorics
Problem Statement
Each of the 450 members of a parliament gives a slap in the face to exactly one of his colleagues. Prove that after that they can choose a committee consisting of 150 members, none of whom has been slapped in the face by any other member of the committee.(Folklore)