#############################################################

import sys
sys.setrecursionlimit(10**7)

from heapq import heappop,heappush
from collections import deque,defaultdict,Counter
from bisect import bisect_left, bisect_right
from itertools import product,combinations,permutations

ipt = sys.stdin.readline

def iin():
    return int(ipt())
def lmin():
    return list(map(int,ipt().split()))

MOD = 998244353
#############################################################

N,P,K = lmin()
L = [lmin() for _ in range(N)]

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

for t,b in L:
    ndp = dp[:]
    for j in range(K):
        if dp[j] == -1:
            break
        if t == 1:
            ndp[j+1] = max(ndp[j+1],dp[j]+b)
        else:
            ndp[j+1] = max(ndp[j+1],dp[j]*2)
    dp = ndp
    if max(dp) > 10**18:
        print(-1)
        exit()

print(max(dp))