q=[[-1]*1000 for i in range(1000)]
for M in range(1000):
  for i in range(1000):
    j=(M*i)%1000
    if q[M][j]==-1:
      q[M][j]=M*i

T=int(input())
for _ in range(T):
  X,M=map(int,input().split())
  ans=-1
  Y=X*(10**15)
  Y+=(-Y)%M
  Y+=q[M%1000][(X-Y)%1000]
  lx=len(str(X))
  ly=len(str(Y))
  if Y%M==0 and lx<=ly<=18 and str(Y)[:lx]==str(Y)[-lx:]==str(X):
    ans=Y
  print(ans)