using System;

using System.Collections.Generic;

public class Program

{

    public static void Main()

    {

        var testSetNoDuplicates = new int[] { 1, 2, 3, 4, 5, 6 };

        var testSetWithDuplicates = new int[] { -1, 1, 2, 3, 4, 5, 6, -1 };

        Console.WriteLine(IsContainsDuplicates(testSetNoDuplicates));

        Console.WriteLine(IsContainsDuplicates(testSetWithDuplicates));

    }

    private static bool IsContainsDuplicates(int[] ints)

    {

        var intsContainer = new HashSet<int>();

        foreach(int i in ints)

        {

            if(intsContainer.Contains(i))

                return true;

            intsContainer.Add(i);

        }

        return false;

    }

}