BALTIC-WAY 2017 Problem 7
Each edge of a complete graph on 30 vertices is coloured either red or blue. It is allowed to choose a nonmonochromatic triangle and change the colour of the two edges of the same colour to make the triangle monochromatic. Prove that by using this operation repeatedly it is possible to make the entire graph monochromatic.
(A complete graph is a graph where any two vertices are connected by an edge.)
Dataset text NuminaMath olympiads. Quoted with source.
Solutions
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