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
	{
		try
		{
		Scanner s=new Scanner(System.in);
		int t=s.nextInt();
		for(int i=0;i<t;i++)
		{
			int a=s.nextInt();
			int b=s.nextInt();
			System.out.println((a%b));
 
		}
		}
		catch(Exception e)
		{
			return ;
		}
 
	}
}

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3 
1 2
100 200
40 15