n, k = map(int, input().split())
a = list(map(int, input().split()))
l = 0
r = a[-1] - a[0] + 1
while r - l > 1:
    x = (r + l) // 2
    cnt = 1
    lst = a[0]
    for i in range(1, n):
        if a[i] - lst >= x:
            lst = a[i]
            cnt += 1
    if cnt >= k:
        l = x
    else:
        r = x
print(l)