B"You are given n non-decreasing arrays of non-negative numbers. Vasya repeats the following operation k times: Vasya wants to maximize the sum of the elements in his pocket. The first line contains two integers n and k ( 1 <= n, k <= 3 ,000 ): the number of arrays and operations. Each of the next n lines contain an array. The first integer in each line is t_i ( 1 <= t_i <= 10^6 ): the size of the i -th array. The following t_i integers a_{i, j} ( 0 <= a_{i, 1} <= ldots <= a_{i, t_i} <= 10^8 ) are the elements of the i -th array. It is guaranteed that k <= sum limits_{i=1}^n t_i <= 10^6 . Print one integer: the maximum possible sum of all elements in Vasya's pocket after k operations. "...