The diagram says that (Cyrillic ∩ Greek) - (Cyrillic ∩ Latin) is 3 letters, П Ф Г but as the sibling comment says, Λ/Л, Δ/Д and Κ/К are similar enough. That only leaves you with Θ/theta (th as in thin), Σ/sigma (s as in soft), Ξ/xi (x as in fox), Ψ/psi (ps as in lapse), and Ω/omega (o as in ore.) A lot of those are close enough that you can sort of guess, if you know the English names for the letters!