n,m=map(int,input().split())
dp=[0]*(m+1)
x=[list(map(int,input().split())) for i in range(n)]
x.sort()
for i,j in x:
    for l in range(m-i,-1,-1):
    	if l*2+i<=m:
    		dp[l*2+i]=max(dp[l*2+i],dp[l]+j)
print(max(dp))