Smallest Shared Migration Tag

Two wildlife sanctuaries each maintain a log of tag numbers for the migratory birds they have recorded, sorted in non-decreasing order (a tag can appear more than once in a log if the same bird was scanned on separate visits). Conservationists studying cross-site movement want to know the smallest tag number that both sanctuaries have ever recorded, since it identifies the earliest-numbered bird confirmed to have visited both sites.

Given the two logs, find the smallest tag number that appears in both of them, or report that no tag number is shared.

Input format

• Line 1: an integer n, the length of the first sanctuary's log.
• Line 2: n space-separated integers, the first log, sorted in non-decreasing order.
• Line 3: an integer m, the length of the second sanctuary's log.
• Line 4: m space-separated integers, the second log, sorted in non-decreasing order.

Output format

Print a single integer: the smallest tag number that appears in both logs, or -1 if no tag number is shared.

Constraints

• 1 <= n, m <= 10^5
• 1 <= tag number <= 10^9
• Both logs are sorted in non-decreasing order and may contain repeated values.

3
1 2 3
2
2 4

2

3
1 2 3
3
4 5 6

-1