

int p1,p2,p3,i,n,j;
char a[1000];
char b[1000];
char c[1000];
int max(int a,int b)
{
	if (a>b) return a;else return b;
}
int za(int m)
{
	if (m<0) return 0;else return a[m]-'0';
}
int zb(int m)
{
	if (m<0) return 0;else return b[m]-'0';
}
int main()
{
	cin>>n;
	for (j=1;j<=n;j++)
	{
		for (i=0;i<=999;i++) {a[i]='\0';b[i]='\0';c[i]='\0';}
		cin>>a;
		cin>>b;
		p1=0;while(a[p1]!='\0')p1++;p1--;
		p2=0;while(b[p2]!='\0')p2++;p2--;
		c[0]=0;
		for (i=0;i<=max(p1,p2)+1;i++) c[i]=za(p1-i)-zb(p2-i);
		for (i=0;i<=max(p1,p2)+1;i++) 
		{
			c[i+1]+=(c[i]+10)/10-1;
			c[i]=(c[i]+10)%10;
		}
		p3=900;while((c[p3]==0)&&(p3>=0))p3--;
		for (i=p3;i>=0;i--) cout<<(int)c[i];
		if (p3<=0) cout<<0;
		cout<<endl;
	}
	return 0;
}

