public static int minimumNumber(int n, string password)
    {
        const int REQ_LENGTH = 6;
        int missing = 0;
        
        string[] tests = [
            // lowercases
            @"[a-z]{1,}", 
            // uppercases
            @"[A-Z]{1,}", 
            // digits
            @"\d{1,}", 
            // special characters
            @"[-!@#$%^&*()+]{1,}"
        ];
        
        foreach (string test in tests) {
            if (!Regex.IsMatch(password, test)) {
                missing++;
            }
        };
        
        return REQ_LENGTH - n > missing ? REQ_LENGTH - n : missing;
    }