INT = lambda : int(input())
MI = lambda : map(int, input().split())
MI_DEC = lambda : map(lambda x : int(x)-1, input().split())
LI = lambda : list(map(int, input().split()))
LI_DEC = lambda : list(map(lambda x : int(x)-1, input().split()))
INF = float('inf')
CEIL = lambda a, b : (a + b - 1) // b

N, P, K = MI()

dp = [[-1]*(K+1) for i in range(N+1)]
dp[0][0] = P

MAX = 10**18
for i in range(N):
    T, B = MI()

    for j in range(K+1):
        dp[i+1][j] = max(dp[i+1][j], dp[i][j])

        if j + 1 > K:
            continue

        if T == 1:
            dp[i+1][j+1] = max(dp[i+1][j+1], dp[i][j] + B)

        else:
            dp[i+1][j+1] = max(dp[i+1][j+1], dp[i][j] * 2)

        if dp[i+1][j+1] > MAX:
            dp[i+1][j+1] = INF


print(-1 if dp[N][K] == INF else dp[N][K])