Triple

题意翻译

## 题目描述 给定一个包含 n 元素的数组 a，输出至少出现三次的任何值，如果没有这样的值，则输出 -1。 ## 输入格式 第一行包含整数 $t$ （$1≤t≤10 ^4$） 测试用例的数量。 每个测试用例的第一行包含一个整数 $n$ （$1≤n≤2⋅10^5$）， 数组的长度。 每个测试用例的第二行包含 $n$ 整数$a_1$、$a_2$、…… $a_n$($1≤a _ i≤n$) 数组的元素。 保证所有测试用例的 $n$ 之和不超过 $2·10^5 $ . ## 输出格式 对于每个测试用例，输出至少出现三次的任何值，如果没有此类值，则输出 -1。

题目描述

Given an array $ a $ of $ n $ elements, print any value that appears at least three times or print -1 if there is no such value.

输入输出格式

输入格式

The first line contains an integer $ t $ ( $ 1 \leq t \leq 10^4 $ ) — the number of test cases. The first line of each test case contains an integer $ n $ ( $ 1 \leq n \leq 2\cdot10^5 $ ) — the length of the array. The second line of each test case contains $ n $ integers $ a_1, a_2, \dots, a_n $ ( $ 1 \leq a_i \leq n $ ) — the elements of the array. It is guaranteed that the sum of $ n $ over all test cases does not exceed $ 2\cdot10^5 $ .

输出格式

For each test case, print any value that appears at least three times or print -1 if there is no such value.

输入输出样例

输入样例 #1

7
1
1
3
2 2 2
7
2 2 3 3 4 2 2
8
1 4 3 4 3 2 4 1
9
1 1 1 2 2 2 3 3 3
5
1 5 2 4 3
4
4 4 4 4

输出样例 #1

-1
2
2
4
3
-1
4

说明

In the first test case there is just a single element, so it can't occur at least three times and the answer is -1. In the second test case, all three elements of the array are equal to $ 2 $ , so $ 2 $ occurs three times, and so the answer is $ 2 $ . For the third test case, $ 2 $ occurs four times, so the answer is $ 2 $ . For the fourth test case, $ 4 $ occurs three times, so the answer is $ 4 $ . For the fifth test case, $ 1 $ , $ 2 $ and $ 3 $ all occur at least three times, so they are all valid outputs. For the sixth test case, all elements are distinct, so none of them occurs at least three times and the answer is -1.