Korovy

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

l = 1
r = coords[-1]

def check(dist, k, coords):
    count = 1
    to_prev = 0
    for i in range(1, len(coords)):
        to_prev += coords[i] - coords[i-1]
        if to_prev >= dist:
            count += 1
            to_prev = 0
    return count >= k


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

print(l)