N = int(input())
vs = sorted(list(map(int, input().split())))

ans = vs[-1]

diffs = []
pre_v = vs[0]
for v in vs[1:]:
    diffs.append(v-pre_v)
    pre_v = v


def f(diffs):


    return diffs

for _ in range(N-2):
    index, m = min(enumerate(diffs), key = lambda x:x[1])

    if index-1 >= 0 :
        diffs[index-1] += m/2
    if index+1 < len(diffs):
        diffs[index+1] += m/2

    del diffs[index]

print(ans-diffs[0]/2)