void main()
{
	int l1[25],l2[25],n,w,z,q,i,d,k,j;
/*	int t;
	char c[101]
*/	char c1[25][101],c2[25][101],a[25][101];
	scanf("%d",&n);
	for(i=0;i<n;i++)
	{
		scanf("%s",c1[i]);
		l1[i]=strlen(c1[i]);
		scanf("%s",c2[i]);
		l2[i]=strlen(c2[i]);

		d=l1[i]-l2[i];
		for(w=l2[i];w<l1[i]-1;w++)
			c2[i][w]='0';
		c2[i][l1[i]-1]='\0';
		
		q=0;
		c2[i][l1[i]]='\0';
		c2[i][l1[i]-1]='0';
		while(q!=d)
		{
			for (z=l1[i];z>0;z--)
			{
				c2[i][z]=c2[i][z-1];
			}
			c2[i][0]=c2[i][l1[i]];
			q++;
		}
		c2[i][l1[i]]='\0';




		for(k=l1[i]-1;k>=0;k--)
		{
			if(c1[i][k]>=c2[i][k]) 
				a[i][k]=c1[i][k]-c2[i][k]+48;
			else 
			{
				a[i][k]=c1[i][k]+10-c2[i][k]+48;
				c1[i][k-1]=c1[i][k-1]-1;
			}
		}
		
	}
	for(i=0;i<n;i++)
	{
		for(j=0;j<l1[i];j++)
			printf("%c",a[i][j]);
		printf("\n");
	}
}
