text: n = int(input())
  speed_dist = []
  for i in range(n):
      temp_arr = []
      s = input()
      temp_arr.append(int(s.split(" ")[0]))
      temp_arr.append(int(s.split(" ")[1]))
      speed_dist.append(temp_arr)
  
  speed_dist.sort()
  
  x = -1
  for i in range(1, n):
      time_diff = speed_dist[i][0] - speed_dist[i - 1][0]
      dist_diff = abs(speed_dist[i][1] - speed_dist[i - 1][1])
      speed = dist_diff/time_diff
      if speed > x:
          x = speed
  print(x)