import java.io.*;
import java.util.HashSet;
import java.util.InputMismatchException;
import java.util.Set;

public class C {
    public static void main(String []args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        OutputWriter out = new OutputWriter(outputStream);

        int cases = Integer.parseInt(in.next());
        Solution sol = new Solution();

        while (cases > 0) {
            int n = Integer.parseInt(in.next());
            int [] arr = IOUtils.readIntArray(in, n);
            System.out.println(sol.minSubArray(n, arr));

            cases--;
        }
    }
}

class Solution {
    public int minSubArray(int n, int [] arr) {
        if (n == 1) return -1;
        Set<Integer> set = new HashSet<>();
        int left = 0;
        int i = 0;
        int minLen = Integer.MAX_VALUE;
        while (i < n) {
            if (!set.contains(arr[i])) {
                set.add(arr[i]);
                i++;
                continue;
            }
            minLen = Math.min(minLen, i - left + 1);
            if (minLen == 2) return 2;

            while (arr[left] != arr[i]) {
                set.remove(arr[left]);
                left++;
                minLen = Math.min(minLen, i - left + 1);
            }
            set.remove(arr[left++]);
        }
        return minLen;
    }
}

class InputReader {

    private InputStream stream;
    private byte[] buf = new byte[1024];
    private int curChar;
    private int numChars;
    private SpaceCharFilter filter;

    public InputReader(InputStream stream) {
        this.stream = stream;
    }

    public int read() {
        if (numChars == -1)
            throw new InputMismatchException();
        if (curChar >= numChars) {
            curChar = 0;
            try {
                numChars = stream.read(buf);
            } catch (IOException e) {
                throw new InputMismatchException();
            }
            if (numChars <= 0)
                return -1;
        }
        return buf[curChar++];
    }

    public int readInt() {
        int c = read();
        while (isSpaceChar(c))
            c = read();
        int sgn = 1;
        if (c == '-') {
            sgn = -1;
            c = read();
        }
        int res = 0;
        do {
            if (c < '0' || c > '9')
                throw new InputMismatchException();
            res *= 10;
            res += c - '0';
            c = read();
        } while (!isSpaceChar(c));
        return res * sgn;
    }

    public String readString() {
        int c = read();
        while (isSpaceChar(c))
            c = read();
        StringBuilder res = new StringBuilder();
        do {
            if (Character.isValidCodePoint(c))
                res.appendCodePoint(c);
            c = read();
        } while (!isSpaceChar(c));
        return res.toString();
    }

    public boolean isSpaceChar(int c) {
        if (filter != null)
            return filter.isSpaceChar(c);
        return isWhitespace(c);
    }

    public static boolean isWhitespace(int c) {
        return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }

    public String next() {
        return readString();
    }

    public interface SpaceCharFilter {
        public boolean isSpaceChar(int ch);
    }
}

class OutputWriter {
    private final PrintWriter writer;

    public OutputWriter(OutputStream outputStream) {
        writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
    }

    public OutputWriter(Writer writer) {
        this.writer = new PrintWriter(writer);
    }

    public void close() {
        writer.close();
    }

    public void printLine(long i) {
        writer.println(i);
    }

}

class IOUtils {

    public static int[] readIntArray(InputReader in, int size) {
        int[] array = new int[size];
        for (int i = 0; i < size; i++)
            array[i] = in.readInt();
        return array;
    }

}
