-module(common_prime_divisors).
-export([common_prime_divisors/2]).

common_prime_divisors(A, B) ->
    length([ok || {X, Y} <- lists:zip(A, B), has_same_prime_divisors(X, Y)]).

has_same_prime_divisors(X, Y) ->
    D = gcd(X, Y),
    case remove_common(X, D) of
        1 -> remove_common(Y, D) =:= 1;
        _ -> false
    end.

remove_common(1, _) -> 1;
remove_common(N, M) ->
    case gcd(N, M) of
        1 -> N;
        D -> remove_common(N div D, M)
    end.

gcd(N, M) when N rem M =:= 0 -> M;
gcd(N, M) -> gcd(M, N rem M).