def heron(a, b, c):
    s = (a + b + c) * 0.5
    return (s * (s - a) * (s - b) * (s - c)) ** 0.5

a, b, c = map(int, input().split())

S = heron(a, b, c)
r = S / ((a + b + c) / 2)
print(r)