QUEST5  Nail Them
To get to the treasure, Jones must complete one more task. He comes across a table, where there are a number of wooden planks lying along the length of the table. He notices that the width of the table is exactly equal to the width of every plank on it. The planks are so heavy that they cannot be manually moved in any way. Some of these wooden planks are overlapping. Jones has a hammer and the Gods grant him infinite nails. The planks have to be joined to the table with nails such that every plank is connected to the table through at least one nail. The nails are of sufficient length, and have to be hammered vertically into the table. One or more planks can be joined to the table through a single nail provided they have a common overlap. Find out the minimum number of nails he needs to nail all planks to the table.
Input
 The first line of the input is a positive integer t <= 20, denoting the number of tables.
 The descriptions of the table follow one after the other.
 Table description:
 The first line of the description of the k^{th} table contains a positive integer n (n <= 10010), the number of planks on it.
 This is followed by n lines containing the description of the planks.
 The description of each plank is a pair of integers a and b (0 <= a <= b <= 10000010), denoting the distance of the left end and right end of the plank from the left end of the table.
Output
The output must contain t lines , the k^{th} line corresponding to the k^{th} table. The output on the k^{th} line must be an integer i_{k}, the minimum number of nails required.
Example
Input:
2
3
1 5
3 5
2 4
2
1 4
4 5
Output:
1
1
hide comments
sanyajenee02:
20181107 09:02:32
Last edit: 20181111 20:38:41 

Shubham Jadhav:
20170526 13:30:48
Really nice question. AC in one go :) 

sudeep_11:
20170204 15:42:21
Just a small modification in solution of BUSYMAN and its done ! 

blazekid_dtu:
20160407 14:44:26
solve BUSYMAN before this. 

gratitude:
20150308 13:49:39
similar to interval scheduling problem 

N0VICE:
20140914 15:32:35
Nice and easy :) 

Archit Jain:
20140912 15:11:01
too easy


Matija MartiniĆ¦:
20140527 19:58:43
same doubt...


Rajarshi Sarkar:
20130510 12:44:34
1 4


npsabari:
20130120 11:42:22
Nice problem! 
Added by:  Kashyap KBR 
Date:  20051208 
Time limit:  0.465s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: NODEJS PERL6 VB.NET 