import sys
input = sys.stdin.readline

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

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

Y=X[:-20]
REST=X[-20:]

ANS=0
for v,w in Y:
    if w<=M:
        ANS+=v
        M-=w

Q=[(0,0)]

for v,w in REST:
    NQ=[]
    for x,y in Q:
        if w+y<=M:
            NQ.append((v+x,w+y))

    Q+=NQ

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

print(ANS+MAX)