T=int(input())
for _ in range(T):
  n,K=map(int,input().split())
  for i in range(300):
    x=n-i
    if x==0:
      print(-1)
      break
    f=1
    for y in range(1,x+1):
      if y*y>x:
        break
      if x%y==0 and y<=K and x//y<=K:
        f=0
    if f:
      print(x)
      break
  else:
    print(-1)