We initiate an approach to simultaneously treat numerators and denominators of Green's functions arising from quasi-periodic Schrödinger operators, which in particular allows us to study completely resonant phases of the almost Mathieu operator.Let (H λ,α,θ u)(n) = u(n + 1) + u(n − 1) + 2λ cos 2π(θ + nα)u(n) be the almost Mathieu operator on ℓ 2 (Z), where λ, α, θ ∈ R. LetWe prove that for any θ with 2θ ∈ αZ + Z, H λ,α,θ satisfies Anderson localization if |λ| > e 2β(α) . This confirms a conjecture of Avila and Jitomirskaya [The