void c(char a[],int h,char b[],int k)
{
	int i,j,w=0,y=0;
	char c[252];
	for(i=h-1,j=k-1;i>=0;i--,j--)
	{
		if(j>=0)
		{
		c[i+1]=a[i]+48-b[j];
		if(c[i+1]<48)
		{
			c[i+1]=c[i+1]+10;
			a[i-1]=a[i-1]-1;
		}
		}
		else
		{
			if(a[i]<48)
			{c[i+1]=a[i]+10;
			a[i-1]=a[i-1]-1;}
			else
			c[i+1]=a[i];}
	}
	
	for(i=1;i<h+1;i++)
	{
        if(c[i]!='0')
		{w=1;y++;}
        if(h+1==2||y!=0)
		{printf("%c",c[i]);}}
	printf("\n");
	
	
}

int main()
{
    int h,k,n,i;
	char a[251],b[251];
    scanf("%d",&n);
	for(i=0;i<n;i++)
	{
		scanf("%s%s\n",a,b);
	    h=strlen(a);
     	k=strlen(b);
	    if(h>=k)
		  c(a,h,b,k);
	    else if(k>h)
		  c(b,k,a,h);
	}
	return 0;

}