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

def calc(a, b, c): # a を選んだ場合の期待値
    re = 0
    re += a * (1/2) * (1 if a >= c * 2 else 0)
    re += a * (1/2) * (1 if a >= b * 2 else 0)
    re += c * (0 if a >= b * 2 else 1)
    re += b * (0 if a >= c * 2 else 1)
    return re / (a + b + c)

print(max(calc(p, q, r), calc(q, r, p), calc(r, p, q)))