A, B = map(int, input().split())
A = abs(A)
B = abs(B)
if A == 0 or B == 0:
    if A == 0 and B == 0:
        print(0.25)
    else:
        m = max(A, B)
        S = 1/4
        for i in range(102, 2, -1):
            if (i - 1) % m == 0:
                S += ((i - 1) // m + 1) / pow(i, i)
        print(S)
else:
    S = 0
    L = [[0 for _ in range(101)] for __ in range(101)]
    F = [0 for _ in range(101)]
    for i in range(-40, 40):
        for j in range(-40, 40):
            for k in range(-40, 40):
                for l in range(-40, 40):
                    if i % 2 == l % 2 and j % 2 == k % 2:
                        p = 1 + i * A + j * B
                        q = 1 + k * A + l * B
                        if 0 < p < 100 and 0 < q < 100 and 1 < p + q < 100:
                            L[p][q] = 1
    for i in range(100, 0, -1):
        for j in range(100, 0, -1):
            if i + j <= 100:
                F[i+j] += L[i][j]
    for i in range(100, 1, -1):
        S += F[i] / pow(i, i)
    print(S)