n,p,k=map(int,input().split())
dp=[-1]*(k+1)
dp[0]=p
for i in range(n):
  a,b=map(int,input().split())
  if a==1:
    for j in range(1,k+1):
      if dp[-j-1]==-1:
        continue
      dp[-j]=max(dp[-j],dp[-j-1]+b)
      if dp[-j]>10**18:
        print(-1)
        exit()
  else:
    for j in range(1,k+1):
      if dp[-j-1]==-1:
        continue
      dp[-j]=max(dp[-j],dp[-j-1]*2)
      if dp[-j]>10**18:
        print(-1)
        exit()
        
print(dp[-1])