First Non-Repeating Element Index

First Non-Repeating Element Index

Find the first element that appears exactly once.

Input format

The first line has one integer N. The second line has N space-separated integers.

Output format

Print the 0-based index of the first element whose value appears exactly once. If every value repeats, print -1.

Constraints

• Values fit in a 64-bit signed integer
• Trailing whitespace and a trailing newline are ignored by the judge

Read from stdin, write to stdout. Sample cases below show the exact format.

4
1 2 1 3

1

4
1 1 2 2

-1