n, w = map(int, input().split())
ms = [tuple(map(int, input().split())) for _ in range(n)]

l = 0
h = 3 * 10**9
for _ in range(64):
    m = (l + h) / 2
    total = 0
    for s, t in ms:
        milling = m - 2 * t
        if milling > 0:
            total += milling * s
    if total >= w:
        h = m
    else:
        l = m
print(l)