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ƒ: (ℝ \ (-1,1) , Bor(ℝ \ (-1,1) , λ) → A ∈ Bor(ℝ)

ƒ(x) = ∑ 2/[x] * χ[n, n + 1/n) , n ∈ ℕ \ {0}

∫ƒdλ(x) = ?

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