import math


def capital_f(n):
    k = 0.81 / 0.19
    ll = 0.9 / 0.1
    if math.isinf(n):
        return math.sqrt(k) / ll
    else:
        return math.sqrt(k * (1 - 0.81 ** n)) / (ll * (1 - 0.9 ** n))


def small_f(n):
    res = 1200 * (capital_f(n) - capital_f(math.inf))
    res /= capital_f(1) - capital_f(math.inf)
    return res


def g(x):
    return 2.0 ** (x / 800)


def inv_g(x):
    return 800 * math.log2(x)


def rating(n, ps):
    in_par = sum(g(ps[i]) * (0.9 ** (i + 1)) for i in range(n))
    in_par /= sum(0.9 ** (i + 1) for i in range(n))
    return round(inv_g(in_par) - small_f(n))


def main():
    n = int(input())
    ps = [int(input()) for _ in range(n)]
    print(rating(n, ps))


if __name__ == "__main__":
    main()