Grandma Capa has decided to knit a scarf and asked Grandpa Sher to make a pattern for it, a pattern is a string consisting of lowercase English letters. Grandpa Sher wrote a string s of length n.

Grandma Capa wants to knit a beautiful scarf, and in her opinion, a beautiful scarf can only be knit from a string that is a palindrome. She wants to change the pattern written by Grandpa Sher, but to avoid offending him, she will choose one lowercase English letter and erase some (at her choice, possibly none or all) occurrences of that letter in string s.

She also wants to minimize the number of erased symbols from the pattern. Please help her and find the minimum number of symbols she can erase to make string s a palindrome, or tell her that it's impossible. Notice that she can only erase symbols equal to the one letter she chose.

A string is a palindrome if it is the same from the left to the right and from the right to the left. For example, the strings 'kek', 'abacaba', 'r' and 'papicipap' are palindromes, while the strings 'abb' and 'iq' are not.

Input

The first line contains a single integer t (1 ≤ t ≤ 100) — the number of test cases. The next 2 ⋅ t lines contain the description of test cases. The description of each test case consists of two lines.

The first line of each test case contains a single integer n (1 ≤ n ≤ 10^5) — the length of the string.

The second line of each test case contains the string s consisting of n lowercase English letters.

It is guaranteed that the sum of n over all test cases does not exceed 2 ⋅ 10^5.

Output

For each test case print the minimum number of erased symbols required to make the string a palindrome, if it is possible, and -1, if it is impossible.

Example

Input


5
8
abcaacab
6
xyzxyz
4
abba
8
rprarlap
10
khyyhhyhky


Output


2
-1
0
3
2

Note

In the first test case, you can choose a letter 'a' and erase its first and last occurrences, you will get a string 'bcaacb', which is a palindrome. You can also choose a letter 'b' and erase all its occurrences, you will get a string 'acaaca', which is a palindrome as well.

In the second test case, it can be shown that it is impossible to choose a letter and erase some of its occurrences to get a palindrome.

In the third test case, you don't have to erase any symbols because the string is already a palindrome.

import java.io.*;
import java.util.*;

public final class Main {

    static PrintWriter out = new PrintWriter(System.out);
    static FastReader in = new FastReader();
    static Pair[] moves = new Pair[]{new Pair(-1, 0), new Pair(1, 0), new Pair(0, -1), new Pair(0, 1)};
    static int mod = (int) (1e9 + 7);
    static int mod2 = 998244353;

    public static void main(String[] args) {
        int tt = i();
        while (tt-- > 0) {
            solve();
        }
        out.flush();
    }

    public static void solve() {
        int n = i();
        String s = s();
        int ans = -1;
        out:
        for (int i = 0; i < 26; i++) {
            char c = (char) ('a' + i);
            int l = 0;
            int r = n - 1;
            int cur = 0;
            while (l < r) {
                if (s.charAt(l) == s.charAt(r)) {
                    l++;
                    r--;
                } else {
                    if (s.charAt(l) == c) {
                        cur++;
                        l++;
                    } else if (s.charAt(r) == c) {
                        cur++;
                        r--;
                    } else {
                        continue out;
                    }
                }
            }
            ans = (ans == -1) ? cur : Math.min(ans, cur);
        }
        out.println(ans);
    }


    static long[] pre(int[] a) {
        long[] pre = new long[a.length + 1];
        pre[0] = 0;
        for (int i = 0; i < a.length; i++) {
            pre[i + 1] = pre[i] + a[i];
        }
        return pre;
    }

    static void print(char A[]) {
        for (char c : A) {
            out.print(c);
        }
        out.println();
    }

    static void print(boolean A[]) {
        for (boolean c : A) {
            out.print(c + " ");
        }
        out.println();
    }

    static void print(int A[]) {
        for (int c : A) {
            out.print(c + " ");
        }
        out.println();
    }

    static void print(long A[]) {
        for (long i : A) {
            out.print(i + " ");
        }
        out.println();
    }

    static void print(List<Integer> A) {
        for (int a : A) {
            out.print(a + " ");
        }
    }

    static int i() {
        return in.nextInt();
    }

    static long l() {
        return in.nextLong();
    }

    static String s() {
        return in.nextLine();
    }

    static int[][] inputWithIdx(int N) {
        int A[][] = new int[N][2];
        for (int i = 0; i < N; i++) {
            A[i] = new int[]{i, in.nextInt()};
        }
        return A;
    }

    static int[] input(int N) {
        int A[] = new int[N];
        for (int i = 0; i < N; i++) {
            A[i] = in.nextInt();
        }
        return A;
    }

    static long[] inputLong(int N) {
        long A[] = new long[N];
        for (int i = 0; i < A.length; i++) {
            A[i] = in.nextLong();
        }
        return A;
    }

    static int GCD(int a, int b) {
        if (b == 0) {
            return a;
        } else {
            return GCD(b, a % b);
        }
    }

    static long GCD(long a, long b) {
        if (b == 0) {
            return a;
        } else {
            return GCD(b, a % b);
        }
    }

    static long LCM(int a, int b) {
        return (long) a / GCD(a, b) * b;
    }

    static long LCM(long a, long b) {
        return a / GCD(a, b) * b;
    }

    static void shuffleAndSort(int[] arr) {
        for (int i = 0; i < arr.length; i++) {
            int rand = (int) (Math.random() * arr.length);
            int temp = arr[rand];
            arr[rand] = arr[i];
            arr[i] = temp;
        }
        Arrays.sort(arr);
    }

    static void shuffleAndSort(int[][] arr, Comparator<? super int[]> comparator) {
        for (int i = 0; i < arr.length; i++) {
            int rand = (int) (Math.random() * arr.length);
            int[] temp = arr[rand];
            arr[rand] = arr[i];
            arr[i] = temp;
        }
        Arrays.sort(arr, comparator);
    }

    static void shuffleAndSort(long[] arr) {
        for (int i = 0; i < arr.length; i++) {
            int rand = (int) (Math.random() * arr.length);
            long temp = arr[rand];
            arr[rand] = arr[i];
            arr[i] = temp;
        }
        Arrays.sort(arr);
    }

    static boolean isPerfectSquare(double number) {
        double sqrt = Math.sqrt(number);
        return ((sqrt - Math.floor(sqrt)) == 0);
    }

    static void swap(int A[], int a, int b) {
        int t = A[a];
        A[a] = A[b];
        A[b] = t;
    }

    static long pow(long a, long b, int mod) {
        long pow = 1;
        long x = a;
        while (b != 0) {
            if ((b & 1) != 0) {
                pow = (pow * x) % mod;
            }
            x = (x * x) % mod;
            b /= 2;
        }
        return pow;
    }

    static long pow(long a, long b) {
        long pow = 1;
        long x = a;
        while (b != 0) {
            if ((b & 1) != 0) {
                pow *= x;
            }
            x = x * x;
            b /= 2;
        }
        return pow;
    }

    static long modInverse(long x, int mod) {
        return pow(x, mod - 2, mod);
    }

    static boolean isPrime(long N) {
        if (N <= 1) {
            return false;
        }
        if (N <= 3) {
            return true;
        }
        if (N % 2 == 0 || N % 3 == 0) {
            return false;
        }
        for (int i = 5; i * i <= N; i = i + 6) {
            if (N % i == 0 || N % (i + 2) == 0) {
                return false;
            }
        }
        return true;
    }

    public static String reverse(String str) {
        if (str == null) {
            return null;
        }
        return new StringBuilder(str).reverse().toString();
    }

    public static String repeat(char ch, int repeat) {
        if (repeat <= 0) {
            return "";
        }
        final char[] buf = new char[repeat];
        for (int i = repeat - 1; i >= 0; i--) {
            buf[i] = ch;
        }
        return new String(buf);
    }

    public static int[] manacher(String s) {
        char[] chars = s.toCharArray();
        int n = s.length();
        int[] d1 = new int[n];
        for (int i = 0, l = 0, r = -1; i < n; i++) {
            int k = (i > r) ? 1 : Math.min(d1[l + r - i], r - i + 1);
            while (0 <= i - k && i + k < n && chars[i - k] == chars[i + k]) {
                k++;
            }
            d1[i] = k--;
            if (i + k > r) {
                l = i - k;
                r = i + k;
            }
        }
        return d1;
    }

    public static int[] kmp(String s) {
        int n = s.length();
        int[] res = new int[n];
        for (int i = 1; i < n; ++i) {
            int j = res[i - 1];
            while (j > 0 && s.charAt(i) != s.charAt(j)) {
                j = res[j - 1];
            }
            if (s.charAt(i) == s.charAt(j)) {
                ++j;
            }
            res[i] = j;
        }
        return res;
    }
}

class Pair {

    int i, j;

    Pair(int i, int j) {
        this.i = i;
        this.j = j;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        Pair pair = (Pair) o;
        return i == pair.i && j == pair.j;
    }

    @Override
    public int hashCode() {
        return Objects.hash(i, j);
    }
}

class FastReader {

    BufferedReader br;
    StringTokenizer st;

    public FastReader() {
        br = new BufferedReader(new InputStreamReader(System.in));
    }

    String next() {
        while (st == null || !st.hasMoreElements()) {
            try {
                st = new StringTokenizer(br.readLine());
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return st.nextToken();
    }

    int nextInt() {
        return Integer.parseInt(next());
    }

    long nextLong() {
        return Long.parseLong(next());
    }

    double nextDouble() {
        return Double.parseDouble(next());
    }

    String nextLine() {
        String str = "";
        try {
            str = br.readLine();
        } catch (IOException e) {
            e.printStackTrace();
        }
        return str;
    }
}

class Node {

    int data, open, close;

    Node() {
        this(0, 0, 0);
    }

    Node(int data, int open, int close) {
        this.data = data;
        this.open = open;
        this.close = close;
    }
}

class ST {

    int n;
    Node[] st;

    ST(int n) {
        this.n = n;
        st = new Node[4 * Integer.highestOneBit(n)];
    }

    void build(Node[] nodes) {
        build(0, 0, n - 1, nodes);
    }

    private void build(int id, int l, int r, Node[] nodes) {
        if (l == r) {
            st[id] = nodes[l];
            return;
        }
        int mid = (l + r) >> 1;
        build((id << 1) + 1, l, mid, nodes);
        build((id << 1) + 2, mid + 1, r, nodes);
        st[id] = comb(st[(id << 1) + 1], st[(id << 1) + 2]);
    }

    void update(int i, Node node) {
        update(0, 0, n - 1, i, node);
    }

    private void update(int id, int l, int r, int i, Node node) {
        if (i < l || r < i) {
            return;
        }
        if (l == r) {
            st[id] = node;
            return;
        }
        int mid = (l + r) >> 1;
        update((id << 1) + 1, l, mid, i, node);
        update((id << 1) + 2, mid + 1, r, i, node);
        st[id] = comb(st[(id << 1) + 1], st[(id << 1) + 2]);
    }

    Node get(int x, int y) {
        return get(0, 0, n - 1, x, y);
    }

    private Node get(int id, int l, int r, int x, int y) {
        if (x > r || y < l) {
            return new Node();
        }
        if (x <= l && r <= y) {
            return st[id];
        }
        int mid = (l + r) >> 1;
        return comb(get((id << 1) + 1, l, mid, x, y), get((id << 1) + 2, mid + 1, r, x, y));
    }

    Node comb(Node a, Node b) {
        if (a == null) {
            return b;
        }
        if (b == null) {
            return a;
        }
        int min = Math.min(a.open, b.close);
        return new Node(a.data + b.data + min * 2, a.open + b.open - min, a.close + b.close - min);
    }
}