N,P,K=map(int,input().split())
L1=[]
L2=[]
dp=[[0]*(K+1) for i in range(N+1)]
dp[0][0]=P
for i in range(N):
  t,b=map(int,input().split())
  if t==1:
    for j in range(K+1):
      if j<K:
        dp[i+1][j+1]=max(dp[i+1][j+1],dp[i][j]+b)
        if dp[i+1][j+1]>10**18:
          print(-1)
          exit()
      dp[i+1][j]=max(dp[i][j],dp[i+1][j])
  else:
    for j in range(K+1):
      if j<K:
        dp[i+1][j+1]=max(dp[i+1][j+1],dp[i][j]*2)
        if dp[i+1][j+1]>10**18:
          print(-1)
          exit()
      dp[i+1][j]=max(dp[i][j],dp[i+1][j])
print(dp[N][K])