def f(s): k="" for j in range(len(s)-1,-1,-1): k+=s[j] return k n=int(input()) l=[] for i in range (n): a,b=map(int,input().split()) arr=[] arr.append(a) arr.append(b) l.append(arr) for i in l: r=i[0]+i[1] sk=f(str(r)) si1=f(str(i[0])) si2=f(str(i[1])) rt=int(si1)+int(si2) if int(sk)==rt: print(r) else: print("NO")