ISL 2009 C7
A grasshopper jumps along the real axis. He starts at point 0 and makes 2009 jumps to the right with lengths in an arbitrary order. Let be a set of 2008 positive integers less than 1005 - 2009. Prove that the grasshopper can arrange his jumps in such a way that he never lands on a point from . Variant 2. Let be a nonnegative integer. A grasshopper jumps along the real axis. He starts at point 0 and makes jumps to the right with pairwise different positive integral lengths in an arbitrary order. Let be a set of positive integers in the interval , where . Prove that the grasshopper can arrange his jumps in such a way that he never lands on a point from .
Official text Transcription from NuminaMath olympiads, checked word for word against the official paper. Quoted with source.
Official text: IMO 2009 Shortlist booklet, page 9.
Solutions
Official solution Solution 1 by the IMO Problem Selection Committee
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