AT_abc457_c [ABC457C] Long Sequence

You are given integers $ N $ and $ K $ , along with $ N $ integer sequences $ A_1, A_2, \ldots, A_N $ and a length- $ N $ integer sequence $ C = (C_1, C_2, \ldots, C_N) $ . The length of integer sequence $ A_i $ is $ L_i $ , and $ A_i = (A_{i,1}, A_{i,2}, \ldots, A_{i,L_i}) $ . It is guaranteed that $ \displaystyle 1 \le K \le \sum_{i=1}^N C_iL_i $ . Construct an integer sequence $ B = (B_1, B_2, \ldots, B_{\sum_{i=1}^N C_iL_i}) $ from $ A $ and $ C $ using the following procedure. - Let $ B $ be an integer sequence of length $ 0 $ . - For $ i = 1, 2, \ldots, N $ in this order, perform the following operation: - Do this $ C_i $ times: append $ A_i $ to the end of $ B $ . Find the value of $ B_K $ .

The input is given from Standard Input in the following format: > $ N $ $ K $ $ L_1 $ $ A_{1,1} $ $ A_{1,2} $ $ \ldots $ $ A_{1,L_1} $ $ L_2 $ $ A_{2,1} $ $ A_{2,2} $ $ \ldots $ $ A_{2,L_2} $ $ \vdots $ $ L_N $ $ A_{N,1} $ $ A_{N,2} $ $ \ldots $ $ A_{N,L_N} $ $ C_1 $ $ C_2 $ $ \ldots $ $ C_N $

Output the answer.

### Sample Explanation 1 $ B $ is constructed as follows: - Let $ B = () $ . - Append $ A_1 $ to the end of $ B $ once. We get $ B = (1, 3, 2) $ . - Append $ A_2 $ to the end of $ B $ three times. We get $ B = (1, 3, 2, 3, 3, 3) $ . - Append $ A_3 $ to the end of $ B $ twice. We get $ B = (1, 3, 2, 3, 3, 3, 4, 3, 4, 3) $ . For $ B = (1, 3, 2, 3, 3, 3, 4, 3, 4, 3) $ , we have $ B_9 = 4 $ , so output $ 4 $ . ### Constraints - $ 1 \le N $ - $ 1 \le L_i $ - $ \displaystyle \sum_{i=1}^N L_i \le 2 \times 10^5 $ - $ 1 \le A_{i,j} \le 10^9 $ $ (1 \le j \le L_i) $ - $ 1 \le C_i \le 10^9 $ - $ \displaystyle 1 \le K \le \sum_{i=1}^N C_iL_i $ - All input values are integers.