from collections import deque  
mod=998244353
from sys import stdin, setrecursionlimit
input = stdin.readline
readline = stdin.readline
import math
N,M,K=map(int, stdin.readline().split())
dp=[-1]*(K+1) 
dp[0]=M;f=0
for _ in range(N):
  t,b=map(int, stdin.readline().split())
  ndp=[-1]*(K+1)
  if f==1:
    continue
  for i in range(K+1):
    ndp[i]=max(ndp[i],dp[i])
    if i!=0:
      if t==1:
        ndp[i]=max(ndp[i],dp[i-1]+b)
      else:
        ndp[i]=max(ndp[i],dp[i-1]*2)
  dp=ndp
  if dp[-1]>10**18:
    f=1
if f==1:
  print(-1)
else:
  print(dp[-1])