N, P, K = map(int, input().split())
TB = [list(map(int, input().split())) for _ in range(N)]

dp = [[-1]*(K+1) for _ in range(N+1)]
dp[0][0] = P
limit = 10**18+1
for i in range(N):
    T, B = TB[i]
    for j in range(K+1):
        if dp[i][j] != -1:
            dp[i+1][j] = max(dp[i+1][j], dp[i][j])
            if j < K:
                if T == 1:
                    dp[i+1][j+1] = max(dp[i+1][j+1], dp[i][j]+B)
                    dp[i+1][j+1] = min(dp[i+1][j+1], limit)
                else:
                    dp[i+1][j+1] = max(dp[i+1][j+1], dp[i][j]*2)
                    dp[i+1][j+1] = min(dp[i+1][j+1], limit)

print(dp[-1][-1] if dp[-1][-1] != limit else -1)