Unique Bid Auction
Description
There is a game called "Unique Bid Auction". You can read more about it here: https://en.wikipedia.org/wiki/Unique_bid_auction (though you don't have to do it to solve this problem).
Let's simplify this game a bit. Formally, there are $n$ participants, the $i$-th participant chose the number $a_i$. The winner of the game is such a participant that the number he chose is unique (i. e. nobody else chose this number except him) and is minimal (i. e. among all unique values of $a$ the minimum one is the winning one).
Your task is to find the index of the participant who won the game (or -1 if there is no winner). Indexing is $1$-based, i. e. the participants are numbered from $1$ to $n$.
You have to answer $t$ independent test cases.
The first line of the input contains one integer $t$ ($1 \le t \le 2 \cdot 10^4$) — the number of test cases. Then $t$ test cases follow.
The first line of the test case contains one integer $n$ ($1 \le n \le 2 \cdot 10^5$) — the number of participants. The second line of the test case contains $n$ integers $a_1, a_2, \ldots, a_n$ ($1 \le a_i \le n$), where $a_i$ is the $i$-th participant chosen number.
It is guaranteed that the sum of $n$ does not exceed $2 \cdot 10^5$ ($\sum n \le 2 \cdot 10^5$).
For each test case, print the answer — the index of the participant who won the game (or -1 if there is no winner). Note that the answer is always unique.
Input
The first line of the input contains one integer $t$ ($1 \le t \le 2 \cdot 10^4$) — the number of test cases. Then $t$ test cases follow.
The first line of the test case contains one integer $n$ ($1 \le n \le 2 \cdot 10^5$) — the number of participants. The second line of the test case contains $n$ integers $a_1, a_2, \ldots, a_n$ ($1 \le a_i \le n$), where $a_i$ is the $i$-th participant chosen number.
It is guaranteed that the sum of $n$ does not exceed $2 \cdot 10^5$ ($\sum n \le 2 \cdot 10^5$).
Output
For each test case, print the answer — the index of the participant who won the game (or -1 if there is no winner). Note that the answer is always unique.
Samples
6
2
1 1
3
2 1 3
4
2 2 2 3
1
1
5
2 3 2 4 2
6
1 1 5 5 4 4
-1
2
4
1
2
-1