#include <iostream>
#include <stdio.h>
#include <cstdlib>
using namespace std;
int ceill(double a);
int main()
{
int t,a,b;
scanf("%d",&t);
for(int i=0;i<t;i++)
{
scanf("%d%d",&a,&b);
if(((a>=0)&&(b>0))||((a<=0)&&(b<0))) printf("%d\n",labs(a)%labs(b));
else if(labs(a)%labs(b)==0) printf("0\n");
else
{
int x=ceill((double)a/b);
x*=b;
printf("%d\n",labs(x)-labs(a));
}
}
return 0;
}
int ceill(double a)
{
if((int)(a*10)%10==0) return (int)a;
if(a>0) return (int)a+1;
if(a<0) return (int)a-1;
}
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19
5 2
12 5
5 8
15 5
-12 -5
-12 5
12 -5
1000000 1000000
-1000000 -1000000
1000000 -1000000
-1000000 1000000
999999 1000000
-999999 -1000000
-999999 1000000
999999 -1000000
5 12
-5 -12
-5 12
5 -12