n, m = map(int, input().split())
VW = []
for i in range(n):
    v, w = map(int, input().split())
    VW.append((v, w))
VW.sort(key=lambda x: -x[0])
dp = [0]*(m+1)
ans = 0
for v, w in VW:
    for i in reversed(range(m+1)):
        if i+w <= m:
            ans = max(ans, (dp[i]+v)*v)
            dp[i+w] = max(dp[i+w], dp[i]+v)
print(ans)