# coding: utf-8
import math
def II(): return int(input())
def ILI(): return list(map(int, input().split()))


def read():
    N = II()
    RPerf = [II() for __ in range(N)]
    return N, RPerf


def solve(N, RPerf):
    F_inf_upper = math.sqrt(0.81 / (1 - 0.81))
    F_inf_under = 0.9 / (1 - 0.9)
    F_inf = F_inf_upper / F_inf_under

    F_n_upper = math.sqrt(0.81 * (1 - pow(0.81, N)) / (1 - 0.81))
    F_n_under = (0.9 * (1 - pow(0.9, N)) / (1 - 0.9))
    F_n = F_n_upper / F_n_under

    F_1 = 1
    f_n = ((F_n - F_inf) / (F_1 - F_inf)) * 1200

    g_1_upper = 0
    for ind, r in enumerate(RPerf):
        g_1_upper += pow(2, r / 800) * pow(0.9, ind + 1)
    g_1_under = F_n_under

    ans = 800 * math.log2(g_1_upper / g_1_under) - f_n

    return ans


def main():
    params = read()
    print(solve(*params))


if __name__ == "__main__":
    main()