INF = 1 << 60

n, m = map(int, input().split())
items = [list(map(int, input().split())) for _ in range(n)]

items.sort(key=lambda x: x[0])

ans = 0
dp = [- INF for _ in range(m + 1)]
dp[0] = 0
for _ in range(n):
  v, w = items.pop()
  for i in range(m - w, -1, -1):
    ans = max(ans, v * (dp[i] + v))
    dp[i + w] = max(dp[i + w], dp[i] + v)

print(ans)