A10141 | Restaurant

A 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 $l_{i}$ and the finish time $r_{i}$ ( $l_{i}<=r_{i}$ ).

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.

The first line contains integer number $n$ ( $1<=n<=5·10^{5}$ ) — number of orders. The following $n$ lines contain integer values $l_{i}$ and $r_{i}$ each ( $1<=l_{i}<=r_{i}<=10^{9}$ ).

Print the maximal number of orders that can be accepted.