CF1605C.Dominant Character

Ashish has a string $s$ of length $n$ containing only characters 'a', 'b' and 'c'.

He wants to find the length of the smallest substring, which satisfies the following conditions:

• Length of the substring is at least $2$
• 'a' occurs strictly more times in this substring than 'b'
• 'a' occurs strictly more times in this substring than 'c'

Ashish is busy planning his next Codeforces round. Help him solve the problem.

A string $a$ is a substring of a string $b$ if $a$ can be obtained from $b$ by deletion of several (possibly, zero or all) characters from the beginning and several (possibly, zero or all) characters from the end.

阿希什有一个长度为 $n$ 的字符串 $s$，其中仅包含字符 'a'、'b' 和 'c'。

他希望找出满足以下条件的最短子串的长度：

• 该子串的长度至少为 $2$；
• 在该子串中，'a' 出现的次数严格大于 'b' 出现的次数；
• 在该子串中，'a' 出现的次数严格大于 'c' 出现的次数。

阿希什正忙于筹备他的下一场 Codeforces 比赛。请帮助他解决这个问题。

若字符串 $a$ 可通过从字符串 $b$ 的开头删除若干（可能为零或全部）字符，并从结尾删除若干（可能为零或全部）字符而得到，则称 $a$ 是 $b$ 的一个子串。

The first line contains a single integer $t$ $(1 \le t \le 10^{5})$ — the number of test cases. The description of test cases follows.

The first line of each test case contains a single integer $n$ $(2 \le n \le 10^{6})$ — the length of the string $s$.

The second line of each test case contains a string $s$ consisting only of characters 'a', 'b' and 'c'.

It is guaranteed that the sum of $n$ over all test cases does not exceed $10^{6}$.

第一行包含一个整数 $t$（$1 \le t \le 10^{5}$）—— 测试用例的数量。接下来是各测试用例的描述。

每个测试用例的第一行包含一个整数 $n$（$2 \le n \le 10^{6}$）—— 字符串 $s$ 的长度。

每个测试用例的第二行包含一个字符串 $s$，该字符串仅由字符 'a'、'b' 和 'c' 组成。

保证所有测试用例的 $n$ 之和不超过 $10^{6}$。

For each test case, output the length of the smallest substring which satisfies the given conditions or print $-1$ if there is no such substring.

对于每个测试用例，输出满足给定条件的最短子串的长度；若不存在这样的子串，则输出 $-1$。

Consider the first test case. In the substring "aa", 'a' occurs twice, while 'b' and 'c' occur zero times. Since 'a' occurs strictly more times than 'b' and 'c', the substring "aa" satisfies the condition and the answer is $2$. The substring "a" also satisfies this condition, however its length is not at least $2$.

In the second test case, it can be shown that in none of the substrings of "cbabb" does 'a' occur strictly more times than 'b' and 'c' each.

In the third test case, "cacabccc", the length of the smallest substring that satisfies the conditions is $3$.

考虑第一个测试用例。在子串 “aa” 中，字符 'a' 出现了两次，而 'b' 和 'c' 均出现了零次。由于 'a' 的出现次数严格大于 'b' 和 'c' 的出现次数，因此子串 “aa” 满足条件，答案为 $2$。子串 “a” 也满足该条件，但其长度不足 $2$。

在第二个测试用例中，可以证明：字符串 “cbabb” 的任意子串中，'a' 的出现次数均无法严格大于 'b' 和 'c' 各自的出现次数。

在第三个测试用例 “cacabccc” 中，满足条件的最短子串长度为 $3$。