import collections,sys,math,functools,operator,itertools,bisect,heapq,decimal,string,time,random
#sys.setrecursionlimit(10**9)
#sys.set_int_max_str_digits(0)
input = sys.stdin.readline
#n = int(input())
#alist = list(map(int,input().split()))
#alist = []
#s = input()
n,p,k = map(int,input().split())
item =[list(map(int,input().split())) for i in range(n)]

dp = [[-10**18 for i in range(k+1)] for j in range(n+1)]
dp[0][0] = p
for i in range(n):
    for j in range(k+1):
        if dp[i][j] >= 10**18:
            print(-1)
            exit()
        if dp[i][j] == -10**18:
            continue
        dp[i+1][j] = max(dp[i+1][j],dp[i][j])
        if j+1<=k:
            if item[i][0] == 1:
                dp[i+1][j+1] = max(dp[i+1][j+1],dp[i][j] + item[i][1])
            else:
                dp[i+1][j+1] = max(dp[i+1][j+1],dp[i][j] * 2)
print(dp[-1][-1])