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Let (a, b) be a pair of non-negative numbers such that (1)a, b≥1 and (2)a+b≥3. Letu1,...,un be a sequence of vectors from the set {(x, y)εR2: |x|, |y|≤1}, withu1+...+un=0. It is shown that there is a permutation π of indices such that all partial sumsuπ(1)+...+uπ(k) lie in the rectangle |x|≤a, |y|≤b. Conditions (1) and (2) are also necessary.