P, Q, R = map(int, input().split())

a = P / (P + Q + R)
b = Q / (P + Q + R)
c = R / (P + Q + R)

# 当たりを引く確率
x = max(a, b, c)
# ハズレを引く確率
y = 1 - min(a, b, c)

ans = max(x, y)
print(ans)