from operator import itemgetter

N,M=map(int,input().split())

J=[]
for _ in range(N):
    v,w=map(int,input().split())
    J.append((v,w))

J.sort(key=itemgetter(0),reverse=True)

DP=[0]*(M+1)
Ans=0
for v,w in J:
    for x in range(M,w-1,-1):
        Ans=max(Ans,v*(DP[x-w]+v))
        DP[x]=max(DP[x], DP[x-w]+v)

print(Ans)