import java.util.*;
import java.io.*;
import java.text.*;
public class C1257 {

	public static void main(String[] args) throws IOException {
		Scanner sc = new Scanner(System.in);
		PrintWriter pw = new PrintWriter(System.out);
		int t = sc.nextInt();
		while(t-->0) {
			int n = sc.nextInt();
			int [] arr = new int[n];
			ArrayList<Integer> cnt[] = new ArrayList[n+1];
			for (int i = 0; i < cnt.length; i++) {
				cnt[i]=new ArrayList<Integer>();
			}
			for (int i = 0; i < arr.length; i++) {
				arr[i]=sc.nextInt();
				cnt[arr[i]].add(i);
			}
			int min = (int)1e9;
			for(int i=0;i<n+1;i++) {
				for(int j=0;j<cnt[i].size()-1;j++) {
					min = Math.min(-cnt[i].get(j)+cnt[i].get(j+1),min);
				}
			}
			pw.println(min==(int)1e9?-1:min+1);
			
		}
		pw.close();
	}

	static class Scanner {
		StringTokenizer st;
		BufferedReader br;

		public Scanner(InputStream s) {
			br = new BufferedReader(new InputStreamReader(s));
		}

		public Scanner(FileReader r) {
			br = new BufferedReader(r);
		}

		public String next() throws IOException {
			while (st == null || !st.hasMoreTokens())
				st = new StringTokenizer(br.readLine());
			return st.nextToken();
		}

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

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

		public String nextLine() throws IOException {
			return br.readLine();
		}

		public double nextDouble() throws IOException {
			String x = next();
			StringBuilder sb = new StringBuilder("0");
			double res = 0, f = 1;
			boolean dec = false, neg = false;
			int start = 0;
			if (x.charAt(0) == '-') {
				neg = true;
				start++;
			}
			for (int i = start; i < x.length(); i++)
				if (x.charAt(i) == '.') {
					res = Long.parseLong(sb.toString());
					sb = new StringBuilder("0");
					dec = true;
				} else {
					sb.append(x.charAt(i));
					if (dec)
						f *= 10;
				}
			res += Long.parseLong(sb.toString()) / f;
			return res * (neg ? -1 : 1);
		}

		public boolean ready() throws IOException {
			return br.ready();
		}

	}
}
