package com.company.Wrong_Subtraction;

import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] counters=new int[n];
        int[] nums = new int[n*2];
        for (int i = 0; i < n*2; i++) {
            nums[i] = scanner.nextInt();
        }
        for (int i = 0; i < n * 2; i+=2) {
            while(nums[i] % nums[i+1] != 0)
            {
                nums[i]++;
                counters[i/2]++;
            }
            System.out.println(counters[i/2]);
        }
    }
}