output_description: Print the minimum cost to achieve connectivity.
  
  * * *
input_description: The input is given from Standard Input in the following format:
  
      
      
      N
      l_1 r_1
      l_2 r_2
      :
      l_N r_N
attempt: n = int(input())
  a = [list(map(int, input().split())) for i in range(n)]
  dp = [[float("inf")] * (500) for i in range(n + 1)]
  if n > 400:
      exit()
  for i in range(500):
      dp[0][i] = 0
  for i in range(1, n + 1):
      m = a[i - 1][1] - a[i - 1][0]
      mm = a[i - 2][1] - a[i - 2][0]
      for j in range(405):
          for k in range(405):
              if (j <= k and k <= j + m) or (k <= j and j <= k + mm) or i == 1:
                  dp[i][j] = min(dp[i][j], dp[i - 1][k] + abs(j - a[i - 1][0]))
  ans = float("inf")
  for i in range(500):
      ans = min(ans, dp[n][i])
  print(ans)
  
problem_description: Statement
  
  AtCoDeer the deer found N rectangle lying on the table, each with height 1. If
  we consider the surface of the desk as a two-dimensional plane, the i-th
  rectangle i(1≤i≤N) covers the vertical range of [i-1,i] and the horizontal
  range of [l_i,r_i], as shown in the following figure:
  
  ![](https://atcoder.jp/img/arc070/46b7dc61fc2016c9b45f10db46c6fce9.png)
  
  AtCoDeer will move these rectangles horizontally so that all the rectangles
  are connected. For each rectangle, the cost to move it horizontally by a
  distance of x, is x. Find the minimum cost to achieve connectivity. It can be
  proved that this value is always an integer under the constraints of the
  problem.
samples: [{"input": "3\n    1 3\n    5 7\n    1 3", "output": "2\n    \n\nThe second rectangle should be moved to the left by a distance of 2.\n\n* * *"}, {"input": "3\n    2 5\n    4 6\n    1 4", "output": "0\n    \n\nThe rectangles are already connected, and thus no move is needed.\n\n* * *"}, {"input": "5\n    999999999 1000000000\n    1 2\n    314 315\n    500000 500001\n    999999999 1000000000", "output": "1999999680\n    \n\n* * *"}, {"input": "5\n    123456 789012\n    123 456\n    12 345678901\n    123456 789012\n    1 23", "output": "246433\n    \n\n* * *"}, {"input": "1\n    1 400", "output": "0"}]