Problem Statement

There is a 10^9-story building with N ladders.
Takahashi, who is on the 1-st (lowest) floor, wants to reach the highest floor possible by using ladders (possibly none).
The ladders are numbered from 1 to N, and ladder i connects the A_i-th and B_i-th floors. One can use ladder i in either direction to move from the A_i-th floor to the B_i-th floor or vice versa, but not between other floors.
Takahashi can freely move within the same floor, but cannot move between floors without using ladders.
What is the highest floor Takahashi can reach?

Input

The input is given from Standard Input in the following format:
N
A_1 B_1
A_2 B_2
$\ldots$
A_N B_N

Output

Print an integer representing the answer.

Constraints

• $1 \leq N \leq 2 \times 10^5$
• $1 \leq A_i, B_i \leq 10^9$
• $A_i \neq B_i$
• All values in the input are integers.

Sample Input 1

4
1 4
4 3
4 10
8 3

Sample Output 1

10

He can reach the 10-th floor by using ladder 1 to get to the 4-th floor and then ladder 3 to get to the 10-th floor.

Sample Input 2

6
1 3
1 5
1 12
3 5
3 12
5 12

Sample Output 2

12

Sample Input 3

3
500000000 600000000
600000000 700000000
700000000 800000000

Sample Output 3

1

He may be unable to move between floors.

见题面 Input 部分

见题面 Output 部分