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public static class Hebrew
{
    static Dictionary<char, char> mapper = CombineMappers(
        BuildMapper("שנבגקכעיןחלךצמםפ/רדאוה'סטז", "abcdefghijklmnopqrstuvqxyz"),
        BuildMapper("tcdsvuzjyhflknobixgp;m.era,", "אבגדהוזחטיכךלמםנןסעפףצץקרשת"));

    public class CharEqualityIgnoreCase : IEqualityComparer<char>
    {
        public static readonly CharEqualityIgnoreCase Default = new CharEqualityIgnoreCase();

        static int dist = Math.Abs((int)'A' - (int)'a');

        public bool Equals(char x, char y)
        {
            return x == y || (char.IsLetter(x) && char.IsLetter(y) && Math.Abs((int)x - (int)y) == dist);
        }

        public int GetHashCode(char obj)
        {
            return char.IsLetter(obj) ? char.ToLower(obj).GetHashCode() : obj.GetHashCode();
        }
    }

    static Dictionary<char, char> CombineMappers(Dictionary<char, char> mapper1, Dictionary<char, char> mapper2)
    {
        var result = new Dictionary<char, char>(CharEqualityIgnoreCase.Default);

        foreach (var pair in mapper1)
        {
            result.Add(pair.Key, pair.Value);
        }

        foreach (var pair in mapper2)
        {
            result.Add(pair.Key, pair.Value);
        }

        return result;
    }

    static Dictionary<char, char> BuildMapper(string src, string dest)
    {
        var result = new Dictionary<char, char>();

        for (int i = 0; i < src.Length; i++)
        {
            result[src[i]] = dest[i];
        }

        return result;
    }

    public static string Toggle(string text)
    {
        var result = new StringBuilder(text.Length);

        for (int i = 0; i < text.Length; i++)
        {
            var ch = text[i];
            if (mapper.TryGetValue(ch, out ch) == false)
            {
                ch = text[i];
            }

            result.Append(ch);
        }

        return result.ToString();
    }
}