import java.util.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class ar {

    static 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 (final 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 (final IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }

    static boolean[] seen;
    static Map<Integer, Integer> map;
    static Map<Long, Long> lmap;
    static Set<Character> charset;
    static Set<Integer> set;
    static int[] arr;
    static int[][] dp;
    static int rem = (int) 1e9 + 7;
    static List<List<Integer>> graph;
    static int[][] kmv = { { 2, 1 }, { 1, 2 }, { 2, -1 }, { -1, 2 }, { -2, 1 }, { 1, -2 }, { -1, -2 }, { -2, -1 } };
    static char[] car;
    static boolean[] primes;
    static int MAX = (int) 1e4 + 1;
    static double[] dar;
    static long[] lar;
    static long[][] dlar;

    static void Sieve() {
        primes = new boolean[MAX];
        primes[0] = true;
        primes[1] = true;
        for (int i = 2; i * i < MAX; i++) {
            if (!primes[i]) {
                for (int j = i * i; j < MAX; j += i) {
                    primes[j] = true;
                }
            }
        }
    }

    public static void main(String[] args) throws java.lang.Exception {
        FastReader scn = new FastReader();
int t=scn.nextInt();

for(int i=0;i<t;i++){
    int n=scn.nextInt();
    arr=new int[n];
    for(int k=0;k<n;k++)arr[k]=scn.nextInt();

    if(n==1){
        System.out.print(-1+"\n");
        continue;
    }

Map<Integer,Integer> map = new HashMap<>();
map.put(arr[0],0);
int ans=n+1;
for(int k=1;k<n;k++){
if(map.containsKey(arr[k])){
ans=Math.min(k-map.get(arr[k])+1,ans);
map.put(arr[k],k);
}else map.put(arr[k],k);
}
System.out.print(ans==n+1?-1+"\n":ans+"\n");
}

return;
    }
}

