мгновенный

From LSJ

ἀλλ' οὑντυγχάνων τὰ πράγματ' ὀρθῶς ἂν τιθῇ, πράξει καλῶς → but he who makes the best of those events he lights upon will not fare ill

Source

Russian > Greek

ταχύς, ἐξαίφνης, ἀμεριαῖος, στιγμιαῖος