public static int minimumNumber(int n, string password)
{
// Return the minimum number of characters to make the password strong
    List<char> distinctChars = password.Distinct().ToList<char>();

    int charsToBeAdded = 0;

    if(!distinctChars.Exists(x => Char.IsAsciiDigit(x) == true))
    {
        charsToBeAdded++;
    }

    if(!distinctChars.Exists(x => Char.IsAsciiLetterLower(x) == true))
    {
        charsToBeAdded++;
    }

    if(!distinctChars.Exists(x => Char.IsAsciiLetterUpper(x) == true))
    {
        charsToBeAdded++;
    }

    if(!distinctChars.Exists(x => Char.IsAsciiLetterOrDigit(x) == false && Char.IsWhiteSpace(x) == false))
    {
        charsToBeAdded++;
    }

    const int minPasswordLength = 6;

    if(password.Length > minPasswordLength)
    {
        return charsToBeAdded;
    }
    else
    {
        int difference = minPasswordLength - password.Length;

        if(difference > charsToBeAdded)
        {
            return difference;
        }
        else
        {
            return charsToBeAdded;
        }
    }

}