δυοῖν

From LSJ

Ὅσον ζῇς, φαίνου, μηδὲν ὅλως σὺ λυποῦ· πρὸς ὀλίγον ἐστὶ τὸ ζῆν, τὸ τέλος ὁ χρόνος ἀπαιτεῖ. → While you live, shine; have no grief at all; life exists only for a short while, and time demands its toll.

Source

Russian (Dvoretsky)

δυοῖν: gen. и dat. к δύο.