1
n, m = map(int, input().split())
2
f = sorted([int(x) for x in input().split()])
3
 
4
d = f[n - 1] - f[0]
5
for i in range(1, m - n + 1):
6
    d = min(d, f[i + n - 1] - f[i])
7
    
8
print(d)