Problem Statement

We have a sequence X, which is initially empty.
Takahashi has performed the following operation for $i=1,2,\ldots,N$ in this order.

• Append $l_i,l_i+1,\ldots,r_i$ in this order to the end of X.

Find the greatest length of a strictly increasing subsequence of the final X.

Input

The input is given from Standard Input in the following format:
N
l_1 r_1
$\vdots$
l_{N} r_{N}

Output

Print the answer.

Constraints

• $1 \leq N \leq 2 \times 10^5$
• $1 \leq l_i \leq r_i \leq 10^9$
• All values in the input are integers.

Sample Input 1

4
1 1
2 4
10 11
7 10

Sample Output 1

8

The final X is (1,2,3,4,10,11,7,8,9,10).
The 1-st, 2-nd, 3-rd, 4-th, 7-th, 8-th, 9-th, and 10-th elements form a strictly increasing subsequence with the greatest length.

Sample Input 2

4
1 1
1 1
1 1
1 1

Sample Output 2

1

The final X is (1,1,1,1).

Sample Input 3

1
1 1000000000

Sample Output 3

1000000000

见题面 Input 部分

见题面 Output 部分