using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("Hello World");

    }

    static int smallestgap(int[] arr)

    {

        if (arr == null || arr.Length < 2)

    {

        return -1; 

    }

​

    Array.Sort(arr); 

​

    int smallestGap = int.MaxValue;

​

    for (int i = 1; i < arr.Length; i++)

    {

        int gap = arr[i] - arr[i - 1];

        if (gap < smallestGap)

        {

            smallestGap = gap;

        }

    }

​

    return smallestGap; 

    }

}