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
  ans=-1
  for i in range(20):
    Y=X*(10**i)
    Y+=(-Y)%M
    Y+=q[(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
  for i in range(20):
    Y=(X-1)*(10**i)
    Y+=(-Y)%M
    Y+=q[(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)