As we all know, blockchain technology is mostly used to develop a decentralized application. 
A blockchain is a chain of connected block such that each block keeps the hash of its previous block.
You are given a list of blocks represented by pair of numbers. You have to find the maximum length that can be made by connecting these blocks.
The rule for connecting the blocks is:
Suppose a pair (x,y) is followed by (m,n). Then y must be less than m.

 

Input format:

• First line contains n (number of pairs).
• Each of the next n lines contains a and b separated by space of pair (a,b).
• Every pair will be in the form (a,b) where a<b.

Output Format:

Print the maximum length of blockchain that can be made.

Constraint

$1 \le n \le 10^5\\ 1 \le a,b \le 10^5$