You have N items that you want to put them into a knapsack. Item i has value vi and weight wi.

You want to find a subset of items to put such that:

* The total value of the items is as large as possible.
* The items have combined weight at most W, that is capacity of the knapsack.



Find the maximum total value of items in the knapsack.

Constraints

* 1 ≤ N ≤ 40
* 1 ≤ vi ≤ 1015
* 1 ≤ wi ≤ 1015
* 1 ≤ W ≤ 1015

Input


N W
v1 w1
v2 w2
:
vN wN


The first line consists of the integers N and W. In the following N lines, the value and weight of the i-th item are given.

Output

Print the maximum total values of the items in a line.

Examples

Input

4 5
4 2
5 2
2 1
8 3


Output

13


Input

2 20
5 9
4 10


Output

9
"""
半分全列挙
"""
from bisect import bisect
N,W = map(int,input().split())
items = []
for i in range(N):
    v,w = map(int,input().split())
    items.append((v,w))
A = [(0,0)]
for i in range(N//2):
    v,w = items[i]
    A += [(v+x,w+y) for x,y in A]
A.sort(key = lambda x: (x[1],-x[0]))
underV = -1
tmpA = []
for v,w in A:
    if underV < v and w <= W:
        tmpA.append((v,w))
        underV = v
A = tmpA

B = [(0,0)]
for i in range(N//2,N):
    v,w = items[i]
    B += [(v+x,w+y) for x,y in B]
B.sort(key = lambda x: (x[1],-x[0]))
underV = -1
tmpB = []
for v,w in B:
    if underV < v and w <= W:
        tmpB.append((v,w))
        underV = v
B = tmpB

ans = 0
BV,BW = zip(*B)
for v,w in A:
    idx = bisect(BW,W-w)-1
    ans = max(ans,BV[idx]+v)

print(ans)



