from math import ceil
n=int(input())
k=int(input())
v=sorted([int(input()) for i in range(n)])
if n%k==n-1:
    print(ceil(max(sum(v[-(n//k+1):])/(n//k+1)-sum(v[:n//k])/(n//k),sum(v[-(n//k):])/(n//k)-sum(v[:n//k+1])/(n//k+1))))
else:
    print(ceil(sum(v[-(n//k):])/(n//k)-sum(v[:n//k])/(n//k)))