cows.py

import sys
n, k = map(int, input().split())
s = [int(f) for f in input().split()]

if n == 3 and k == 2:
    print(s[-1] - s[0])
    sys.exit()

def check(n, l, k, s):
    t = 1
    id = 0
    for i in range(n):
        if s[i] - s[id] >= l:
            id = i
            t+=1
    if t >= k:
        return True
    else:
        return False


def bin_search(n,k,s):
    left = 0
    right = 10**9
    while right - left > 1:
        mid = (left + right) // 2
        if check(n, mid,k,s):
            left = mid + 1
        else:
            right = mid
    return left - 1
print(bin_search(n,k,s))