import math
n=int(input())
k=int(input())
l=[int(input()) for i in range(n)]
l.sort()
if n==k or n>=k+2:
    a=l[-1]-l[0]
    print(a)
else:
    nl = sorted(l, reverse=True)
    c=l[-1]
    d=sum(l[:2])/2
    
    e=sum(nl[:2])/2
    f=l[0]
    if c-d>e-f:
        print(math.ceil(c-d))
    else:
        print(math.ceil(e-f))