t = int(input())

for _ in range(t):
  n, a = map(int, input().split())
  l, r, mid, res = 0,  n, -1, -1
  t =  2 * (n * a - n)
  while l <= r:
    mid = (l + r) // 2
    if t >= mid * mid - mid:
      res = mid
      l = mid + 1
    else:
      r = mid - 1
  print(res)