import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.util.Map;
import java.util.HashMap;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author masterbios
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        CDominatedSubarray solver = new CDominatedSubarray();
        solver.solve(1, in, out);
        out.close();
    }

    static class CDominatedSubarray {
        transient final int INF = (int) 1e9;

        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int t = in.nextInt();
            while (t-- > 0) {
                int n = in.nextInt();
                int a[] = new int[n];
                for (int i = 0; i < n; i++) a[i] = in.nextInt();
                int ans = INF;
                Map<Integer, Integer> map = new HashMap<>();
                for (int i = 0; i < n; i++) {
                    if (map.containsKey(a[i])) {
                        ans = Math.min(ans, i - map.get(a[i]) + 1);
                    }
                    map.put(a[i], i);
                }
                if (ans == INF) out.println(-1);
                else out.println(ans);
            }
        }

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreElements()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

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

    }
}

