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HMIC 2017 Problem 3

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Let v1,v2,…,vmv_{1}, v_{2}, \ldots, v_{m} be vectors in Rn\mathbb{R}^{n}, such that each has a strictly positive first coordinate. Consider the following process. Start with the zero vector w=(0,0,…,0)∈Rnw=(0,0, \ldots, 0) \in \mathbb{R}^{n}. Every round, choose an ii such that 1≤i≤m1 \leq i \leq m and w⋅vi≤0w \cdot v_{i} \leq 0, and then replace ww with w+viw+v_{i}.

Show that there exists a constant CC such that regardless of your choice of ii at each step, the process is guaranteed to terminate in CC rounds. The constant CC may depend on the vectors v1,…,vmv_{1}, \ldots, v_{m}.

Dataset text NuminaMath olympiads. Quoted with source.

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r \leq \frac{M^{2}}{m^{2}}

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