Since dCn (u1,u2) ≤ dCn (u2,u1), we have dCn (u1,u2) ≤ ⌊ n 2 ⌋, and hence either u1 ∈ Cn[v1 ,v2] or u2 ∈ Cn [v1 ,v2], which contradicts that u1 and u2 ...
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