Variable Sized Arrays

Consider an -element array, , where each index  in the array contains a reference to an array of  integers (where the value of  varies from array to array). See the Explanation section below for a diagram.

Given , you must answer  queries. Each query is in the format i j, where  denotes an index in array  and  denotes an index in the array located at . For each query, find and print the value of element  in the array at location  on a new line.

Click here to know more about how to create variable sized arrays in C++.

Input Format

The first line contains two space-separated integers denoting the respective values of  (the number of variable-length arrays) and  (the number of queries). 
Each line  of the  subsequent lines contains a space-separated sequence in the format k a[i]0 a[i]1 … a[i]k-1describing the -element array located at . 
Each of the  subsequent lines contains two space-separated integers describing the respective values of  (an index in array ) and  (an index in the array referenced by ) for a query.

Constraints

• All indices in this challenge are zero-based.
• All the given numbers are non negative and are not greater than 

Output Format

For each pair of  and  values (i.e., for each query), print a single integer denoting the element located at index  of the array referenced by . There should be a total of  lines of output.

Sample Input

2 2
3 1 5 4
5 1 2 8 9 3
0 1
1 3

Sample Output

5
9

Explanation

The diagram below depicts our assembled Sample Input:

We perform the following  queries:

1. Find the array located at index , which corresponds to . We must print the value at index  of this array which, as you can see, is .
2. Find the array located at index , which corresponds to . We must print the value at index  of this array which, as you can see, is .

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문제가 무엇을 얘기하는지...선뜻 이해가 되지 않는다.

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위의 풀이는 Discussions을 참고하였다.

풀이된 내용을 보면 대충 어떤 문제인지 감이 오긴 한다.

그렇게 어려운 문제가 아닌데도 문제 자체를 이해하지 못하여 난감했다는;;;;