from bisect import bisect

def flatlandSpaceStations(n, c):
    c.sort()
    max_dist = 0
    for city in range(n):
        indx = min(bisect(c, city), len(c) - 1)
        city_dist = min(abs(c[indx] - city), abs(c[max(indx - 1, 0)] - city))
        max_dist = max(max_dist, city_dist)
    return max_dist