import sys
input = sys.stdin.readline

N, P, K = map(int, input().split())
inf = 10 ** 18
pre = [-inf] * (N + 1)
pre[0] = P

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