static int CommonPrimeDivisors(int[] a, int[] b)
{
    long Gcd(long n, long m) => n % m == 0 ? m : Gcd(m, n % m);

    long RemoveCommonPrimeDivisors(long n, long m)
    {
        while (n != 1)
        {
            var d = Gcd(n, m);
            if (d == 1)
            {
                break;
            }
            n /= d;
        }

        return n;
    }

    var counter = 0;
    for (int i = 0; i < a.Length; i++)
    {
        long x = a[i];
        long y = b[i];
        var d = Gcd(x, y);

        x = RemoveCommonPrimeDivisors(x, d);
        if (x != 1)
        {
            continue;
        }

        y = RemoveCommonPrimeDivisors(y, d);
        if (y == 1)
        {
            counter++;
        }
    }

    return counter;
}