static void Main(string[] args)
{
string[] input = Console.ReadLine().Split(' ');
int boys = int.Parse(input[0]);
string[] temp = Console.ReadLine().Split(' ');
List<int> t1 = new List<int>();
for (int i = 0; i < temp.Length; i++)
t1.Add(int.Parse(temp[i]));
int[] p = t1.ToArray();
Array.Sort(p);
int minDiff = 10000000;
if (boys == temp.Length)
Console.WriteLine(p[p.Length - 1] - p[0]);
else
{
for (int i = 0; i < p.Length - 1; i++)
{
for (int a = i + 1; a < p.Length; a++)
{
int t = 0;
for (int b = 0; b < p.Length; b++)
{
if (p[b] >= p[i] && p[b] <= p[a])
t++;
if (t == boys)
{
if (p[a] - p[i] < minDiff)
{
minDiff = p[a] - p[i];
}
break;
}
}
}
}
Console.WriteLine(minDiff);
}
Console.ReadLine();
}
