N, M = map(int, input().split())
dp = [[-1 for _ in range(M + 1)] for c in range(10)]
dp[0][0] = 0
ans = 0
X = []
for i in range(N):
  C, D = map(int, input().split())
  if C == 0: ans += D
  else: X.append((C, D))
X.sort()
X.reverse()
for c, d in X:
  for i in range(9, -1, -1):
    for m in range(M, -1, -1):
      if dp[i][m] == -1:
        continue
      mm = m + ((1 << i) * c)
      if mm <= M:
        dp[i + 1][mm] = max(dp[i + 1][mm], dp[i][m] + d)
res = 0
for i in range(10):
  res = max(res, max(dp[i]))
ans += res
print(ans)