q=[[[] for j in range(1000)] for i in range(1000)]
for M in range(1000):
  for i in range(10000):
    j=(M*i)%1000
    if len(q[M][j])<3:
      q[M][j]+=[M*i]

T=int(input())
for _ in range(T):
  X,M=map(int,input().split())
  ans=-1
  for i in range(20):
    Y=X*(10**i)
    Y+=(-Y)%M
    for v in q[M%1000][(X-Y)%1000]:
      Y+=v
      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
      Y-=v
  for i in range(20):
    Y=(X-1)*(10**i)
    Y+=(-Y)%M
    for v in q[M%1000][(X-Y)%1000]:
      Y+=v
      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
      Y-=v
  print(ans)