n=int(input()) for i in range(n): a,b=input().split() #求反转的和 a1=a[::-1] b1=b[::-1] he1=int(a1)+int(b1) #求和的反转 he2=int(a)+int(b) new_he2=str(he2)[::-1] #判断两者是否相等 if he1==int(new_he2): print(he2) else: print("NO")