Description

There are $n$ segments on the number line. Select $k$ segments from them such that no two segments overlap. Find the maximum possible value of $k$.

Input Format

The first line contains a positive integer $n$;

In the following $n$ lines, each line contains two numbers $a_i$ and $b_i$, describing each segment.

Output Format

Output an integer, the maximum value of $k$.

Sample 1

3
0 2
2 4
1 3

2

Data Range and Hints

For $20\%$ of the data, $n \leq 10$;

For $50\%$ of the data, $n \leq 10^3$;

For $70\%$ of the data, $n \leq 10^5$;

For $100\%$ of the data, $n \leq 10^6$, $0 \leq a_i \lt b_i \leq 10^6$.