N = int(input())
K = int(input())
n = list(int(input()) for _ in range(N))
ans = 0
for bit in range(K**N):
    x = bit
    Group = [[] for _ in range(K)]
    for i in range(N):
        Group[x%K].append(n[i])
        x //= K
    flg = False
    for i in range(K):
        if not Group[i]:
            flg = True
    if flg:
        continue
    Set = []
    for i in range(K):
        Set.append(sum(Group[i]) / len(Group[i]))
    Ma = max(Set)
    Mi = min(Set)
    ans = max(ans, int(Ma - Mi + 0.5))
print(ans)