class Program
{
    static void Main(string[] args)
    {
        var listFruits = new List<string> { "Apple", "Banana", "Apple", "Mango" };
        if (FindDuplicates(listFruits)) { WriteLine($"Yes we find duplicate"); };
        ReadLine();
    }
    public static bool FindDuplicates(List<string> array)
    {
        var dict = new Dictionary<string, int>();
        foreach (var value in array)
        {
            if (dict.ContainsKey(value))
                dict[value]++;
            else
                dict[value] = 1;
        }
        foreach (var pair in dict)
        {
            if (pair.Value > 1)
                return true;
            else
                return false;
        }
        return false;
    }
}