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

ans = 0
tot = 0
for i in range(n):
    tot += s[n-i-1]
    tans = (tot + a[i]) / (i + 1)
    ans = max(ans, tans)
print(ans)