Korova

n, k = map(int, input().split())
s = list(map(int, input().split()))

def check(g, k, s):
    prev = -float('inf')
    i = 0
    while k:
        while s[i] - g < prev:
            i += 1
            if i == len(s):
                return False
        k -= 1
        prev = s[i]
    return True

l = 1
r = s[-1] + 1

while r - l > 1:
    g = l + (r - l) // 2
    if check(g, k, s):
        l = g
    else:
        r = g

print(l)