def solve(p, q):
    dp = [0.0] * 101
    p_win = 1.0/3.0
    dp[p] = 1.0/3.0
    eps = 10**(-9)
    while sum(dp) > eps:
        dp, p_win_delta = update_dp(dp, q)
        p_win += p_win_delta
    return p_win

def update_dp(dp, q):
    new_dp = [0.0] * 101
    pdelta = 0.0
    for i, pi in enumerate(dp):
        pdelta += (i/200 + (100 - i)/300) * pi
        new_dp[max(0, i - q)] += pi*i/200
        new_dp[min(100, i + q)] += pi*(100-i)/300
    return new_dp, pdelta

p, q = map(int, input().split())

print(solve(p, q))