/* package whatever; // don't place package name! */
 
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
	{
Scanner scan = new Scanner(System.in);
 
List<int[]> temp = new ArrayList<>();
while (true) {
    if (!scan.hasNextInt()) break;
    int first = scan.nextInt();
    if (!scan.hasNextInt()) break;
    int second = scan.nextInt();
    temp.add(new int[] { first, second });
}
scan.close();
System.out.println(temp.size());
for (int[] a : temp) {
	System.out.println(a[0]+" "+a[1]);
}
	}
}

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NCA2CjIgMwo0IDgKOSA1Cg==

4 6
2 3
4 8
9 5