N,M = map(int, input().split())
VM = [list(map(int, input().split())) for _ in range(N)]
DP = [0]*(M+1)
VM = sorted(VM, reverse=True, key=lambda x: x[0])
ans = 0
for v,m in VM:
    for i in reversed(range(M)):
        if DP[i]>0 and i+m<=M:
            DP[i+m] = max(DP[i+m],DP[i]+v)
    if m<=M:
        DP[m]=max(DP[m],v)
    ans=max(ans,max(DP)*v)
print(ans)