void Main()

int max = 0;
int count = 1;
int startIndex = 0;
int start=0;
int endIndex=0;
for (int i = 0; i < arr.Length - 2; i++)
{
    startIndex = i;
    while (i<arr.Length-1 && Math.Abs(arr[i] - arr[i + 1]) == 1)
    {
        i++;
        count++;
    }
    if (max < count)
    {
        max=count;
        start=startIndex;
        endIndex=i;
        count=1;

    }



}
for (int k = start; k <= endIndex; k++)
{
    Console.WriteLine(arr[k]);

}