import sys
input = sys.stdin.readline

from operator import itemgetter

N,M=map(int,input().split())
X=[list(map(int,input().split())) for i in range(N)]

M0=M

X.sort(reverse=True)
X.sort(key=lambda x:x[0]/x[1],reverse=True)

ANS=0
LASTS=[]
for i in range(len(X)):
    v,w=X[i]
    if w<=M:
        ANS+=v
        M-=w
        LASTS.append((i,ANS,M))

MMAX=0
for tests in range(25,1000,25):

    if len(LASTS)<tests:
        Q=[(0,0)]
        first=-1
        ANS=0
        M=M0
    else:
        first,ANS,M=LASTS[-tests]
        Q=[(0,0)]
        
    for i in range(first+1,len(X)):
        v,w=X[i]
        NQ=[]
        for x,y in Q:
            if w+y<=M:
                NQ.append((v+x,w+y))

        Q+=NQ

        Q.sort(key=itemgetter(1))

        Q2=[]
        for x,y in Q:
            if Q2 and Q2[-1][0]>=x:
                continue
            else:
                Q2.append((x,y))
        Q=Q2
            

    MAX=0
    for x,y in Q:
        MAX=max(MAX,x)

    if MAX!=MMAX:
        MMAX=MAX
    else:
        break

print(ANS+MMAX)