from itertools import combinations

N = int(input())

K = int(input())

n = [int(input()) for i in range(N)]

n.sort()

ans = 0

for k in combinations(range(1, N), r=K - 1):
    
    x = 0
    
    M = 0
    
    m = 1000
    
    for i in k:
        
        Average = sum(n[x:i]) / (i - x)
        
        m = min(Average, m)
        
        M = max(Average, M)
        
        x = i
        
    Average = sum(n[x:]) / (N - x)
    
    m = min(Average, m)
    
    
    M = max(Average, M)
    
    ans = max(ans, int(M - m))
    
print(ans)