snzl6z3

import math


def A1(s):
    # print math.e
    if s >= 60: return 1.0
    return 1 / (math.pow(math.e, 60 - abs(s)))


def A2(s):
    if s <= 10: return 1.0
    return 1 / (1 + math.pow(math.e, abs(10 - s)))


def B1(s):
    if s >= 0.8: return 1.0
    return 1 / (1 + math.pow(0.2 + s, 3))


def B2(s):
    if 0 <= s <= 0.1: return 1.0
    return 1 / (1 + math.pow(0.9 + s, 2))


def C1(s):
    return 2000


def C2(s):
    return 500


def C3(s):
    return 100


def Rule1_min(s, e):
    return min(A2(s), B2(e))


def Rule2_min(s, e):
    return min(A1(s), B2(e))


def Rule3_min(s, e):
    return min(A1(s), B1(e))


def COG(w, c):
    if len(w) != len(c):
        return -1
    else:
        broitel = 0
        imenitel = 0
        for i in range(len(w)):
            broitel += w[i] * c[i]
            imenitel += w[i]
        return broitel / imenitel


if __name__ == "__main__":
    t = input()
    h = input()

    w = [Rule1_min(t, h), Rule2_min(t, h), Rule3_min(t, h)]
    c = [C1(t), C2(t), C3(t)]

    cog = COG(w, c)
    print cog