INF = float("INF")
N, P, K = map(int, input().split())

items = []
for _ in range(N):
   t, b = map(int, input().split())
   items.append((t, b))

dp = [-INF] * (N+1)
dp[0] = P

U = 10**18


def chmax(A, idx, val):
   if U < val:
      val = INF
   if A[idx] < val:
      A[idx] = val


for i, (t, b) in enumerate(items):
   ndp = dp[:]
   for j in range(i+1):
      if dp[j] < 0:
         continue
      if t == 1:
         chmax(ndp, j+1, dp[j] + b)
      elif t == 2:
         chmax(ndp, j+1, dp[j] * 2)
   dp = ndp


ans = dp[K]
if ans == INF:
   print(-1)
else:
   print(ans)