Solve in Python:
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.


-----Input-----

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).


-----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
r = lambda: map(int, input().split())

n, = r()
a = sorted(tuple(r()) for _ in range(n))[::-1]

ret, left = 0, 10**9 + 1
for l, r in a:
    if r < left:
        ret += 1
        left = l

print(ret)