CF1027F.Session in BSU

普及/提高-

通过率：0%

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题目描述

The first line of the input contains one integer $n$ ( $1 \le n \le 10^6$ ) — the number of exams.

The next $n$ lines contain two integers each: $a_i$ and $b_i$ ( $1 \le a_i < b_i \le 10^9$ ), where $a_i$ is the number of day of the first passing the $i$ -th exam and $b_i$ is the number of day of the second passing the $i$ -th exam.

输入格式

If Polycarp cannot pass all the $n$ exams, print -1. Otherwise print the minimum index of day by which Polycarp can do that.

输出格式

无

输入输出样例

输入#1
```
2
1 5
1 7
```
输出#1
```
5
```
输入#2
```
3
5 13
1 5
1 7
```
输出#2
```
7
```
输入#3
```
3
10 40
40 80
10 80
```
输出#3
```
80
```
输入#4
```
3
99 100
99 100
99 100
```
输出#4
```
-1
```

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