T=int(input())
for _ in range(T):
  X,M=map(int,input().split())
  q=[-1]*1000
  for i in range(1000):
    j=(M*i)%1000
    if q[j]==-1:
      q[j]=M*i
  for i in range(20):
    Y=X*(10**i)
    Y+=(-Y)%M
    Y+=q[(X-Y)%1000]
    if str(Y)[:3]==str(Y)[-3:]==str(X):
      print(Y)
      break
  else:
    print(-1)