Restaurant
题目描述
B. Restaurant
time limit per test
4 secondsmemory limit per test
256 megabytesinput
standard inputoutput
standard outputA restaurant received n orders for the rental. Each rental order reserve the restaurant for a continuous period of time, the i-th order is characterized by two time values − the start time li and the finish time ri (li≤ri).
Restaurant management can accept and reject orders. What is the maximal number of orders the restaurant can accept?
No two accepted orders can intersect, i.e. they can't share even a moment of time. If one order ends in the moment other starts, they can't be accepted both.
Input
The first line contains integer number n (1≤n≤5·105) − number of orders. The following n lines contain integer values li and ri each (1≤li≤ri≤109).
Output
Print the maximal number of orders that can be accepted.
Examples
Input
2
7 11
4 7
Output
1
Input
5
1 2
2 3
3 4
4 5
5 6
Output
3
Input
6
4 8
1 5
4 7
2 5
1 3
6 8
Output
2