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