// "A news aggregator app pulls headlines from k different sources. Each source provides its headlines already sorted by timestamp (earliest first). The app needs to combine all headlines into a single timeline, sorted by timestamp globally.
 
//  Given k sorted arrays, merge them into one sorted array.
//  (1 <= k <= 500; total number of elements across all arrays n <= 10^5; 0 <= element <= 10^9)
 
// Example 1:
//   Input: lists = [[1, 4, 7], [2, 5, 8], [3, 6, 9]]
//   Output: [1, 2, 3, 4, 5, 6, 7, 8, 9]
//   Explanation: Three sources, each sorted. Merged in global order.
 
//  Example 2:
//   Input: lists = [[1, 3, 5], [2, 4, 6], []]
//   Output: [1, 2, 3, 4, 5, 6]
//   Explanation: Third source is empty — just merge the first two. Empty arrays should be handled gracefully.
 
//  Example 3:
//   Input: lists = [[10]]
//   Output: [10]
//   Explanation: Single source with one element.
 
//  Example 4:
//   Input: lists = [[], [], []]
//   Output: []
//   Explanation: All sources are empty.
 
//  Example 5:
//   Input: lists = [[1, 1, 1], [1, 1], [1]]
//   Output: [1, 1, 1, 1, 1, 1]
//   Explanation: Duplicates across sources — all kept, stable relative order."
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		// your code goes here
	}
}

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