def apply(v, t, b):
    return min(10**18+1, v + b if t == 1 else v * 2)


def main():
    n, p, k = map(int, input().split())
    dp = [p] * (k+1)
    for _ in range(n):
        t, b = map(int, input().split())
        for i in range(k, 0, -1):
            dp[i] = max(dp[i], apply(dp[i-1], t, b))
    print(-1 if dp[k] > 10**18 else dp[k])


if __name__ == '__main__':
    main()