#!/usr/bin/env python3


def fits(time):
    return sum(max(0, p * (time - 2 * t)) for p, t in mills) >= w


n, w = map(int, input().split())
mills = [tuple(map(int, input().split())) for _ in range(n)]
low, high = 3, 1e18
while high - low > 1e-6:
    mid = (low + high) / 2
    if fits(mid):
        high = mid
    else:
        low = mid
print(mid)