from fractions import Fraction

C, D = input().split()

b = [False , False, False, True, True]
s = []
# Simplex Algorithm
#     base,               X1,              X2,          X3,          X4,     constant 
s.append([3,  Fraction(3, 4),  Fraction(2, 7), Fraction(1), Fraction(0), Fraction(C)])
s.append([4,  Fraction(1, 4),  Fraction(5, 7), Fraction(0), Fraction(1), Fraction(D)])
s.append([0, Fraction(-1000), Fraction(-2000), Fraction(0), Fraction(0), Fraction(0)])

def base():
    x = -1
    for i in range(1, 5):
        if b[i]:
            continue
        elif s[2][i] < 0:
            if x < 0:
                x = i
            elif s[2][i] < s[2][x]:
                x = i
    return x        

while base() >= 0:
    xb = base()
    b[xb] = True
    u = s[0][5] / s[0][xb]
    v = s[1][5] / s[1][xb]
    if u < v:
        b[s[0][0]] = False
        s[0][0] = xb
        t = s[0][xb]
        for i in range(1, 6):
            s[0][i] /= t
        for j in range(1, 3):
            t = s[j][xb]
            for i in range(1, 6):
                s[j][i] -= t * s[0][i]
    else:
        b[s[1][0]] = False
        s[1][0] = xb
        t = s[1][xb]
        for i in range(1, 6):
            s[1][i] /= t
        for j in range(0, 3):
            if j != 1:
                t = s[j][xb]
                for i in range(1, 6):
                    s[j][i] -= t * s[1][i]
    
# print(s)

ans = float(s[2][5])

print(ans)