The PRO version of the Squid Game is a survival game that includes $456000$ players, numbered from $1$ to $456000$. In the first round, the players will play the "Red Light, Green Light" game, controlled by the doll Hourai. In this game, the doll turns her back and says "Mugunghwa Kkoci Pieot Seumnida", then turns back to face the players. If anyone is moving, they will be eliminated. When all the players have finished, the doll Hourai starts analyzing $m$ pieces of data. The $i$-th data tells that in the players numbered from $l_i$ to $r_i$, exactly one person has been eliminated. Calculate the number of players eliminated. The data guarantees that there is always a correct answer.
### Input
- The first line contains a positive integer $m$.
- The next $m$ lines, the $i$-th line contains two integers $l_i$ and $r_i$.
### Output
- Output the answer to the problem.
### Constraints
- $m \le 2 \cdot 10^5$.
- $1 \le l_i \le r_i \le 456000$ for all $1 \le i \le m$.
### Example
Input
```
5 3
2 5
1 4
3 4
```
Output
```
1
```
