A = list(map(int, input().split()))
SUM = sum(A)
ans = 0

# 印を付ける宝箱を全探索
for i in range(3):
    a = A[i]

    # STAY の場合
    ans = max(ans, a/SUM)

    # CHANGE の場合
    b = A[(i + 1)%3]
    c = A[(i + 2)%3]

    # b or c
    ans = max(ans, (b + c)/(SUM))

print(ans)