import java.util.*;
import java.lang.*;
import java.io.*;
import java.math.BigInteger;
public class Solution
{
    static class Pair{
        int parent;
        int rank;
        Pair(int parent,int rank)
        {
            this.rank=rank;
            this.parent=parent;
        }
    }
    static int find(Pair pr[],int i)
    {
        if(i==pr[i].parent)
            return i;
        else
        {
            pr[i].parent=find(pr,pr[i].parent);
            return pr[i].parent;
        }
    }
    static void join(Pair[] pr,int i,int j)
    {
        i=find(pr,i);
        j=find(pr,j);
        if(i==j)
            return;
        if(pr[i].rank>=pr[j].rank)
        {
            pr[j].parent=i;
            pr[i].rank+=pr[j].rank;
        }
        else
        {
            pr[i].parent = j;
            pr[j].rank+=pr[i].rank;
        }
    }
    static void swap(char ar[],int i,int j)
    {
        char f = ar[i];
        ar[i]=ar[j];
        ar[j]=f;
    }
    static TreeSet<Integer> hs;
    static HashSet<Integer> graph[] ;
	public static void main (String[] args) throws IOException
	{
            StringBuilder sb = new StringBuilder();
            FastReader s1 = new FastReader();
            int t = s1.I();
            while(t--!=0)
            {
                int n =s1.I();
                HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();
                int ar[] = new int[n];
                int len = Integer.MAX_VALUE;
                for(int i=0;i<n;i++)
                {
                    ar[i]=s1.I();
                    if(map.containsKey(ar[i]))
                    {
                        int temp = map.get(ar[i]);
                        int demo = i-temp+1;
                        if(demo<len)
                            len=demo;
                        map.replace(ar[i], i);
                    }
                    else
                    {
                        map.put(ar[i],i);
                    }
                }
                if(len==Integer.MAX_VALUE)
                    sb.append(-1+"\n");
                else
                    sb.append(len+"\n");
            }
            System.out.println(sb);
        }
        static int binary(int left,int right,int ar[],int no)
        {
             int mid=(left+right)/2;
             if(Math.abs(right-left)<=1)
             {
                 if(no>=ar[right])
                 {
                     return right+1;
                 }
                 else if(no<ar[left])
                 {
                     return left;
                 }
                 else
                 {
                      return left+1;
                 }
             }
             if(ar[mid]>no)
             {
                 right=mid-1;
                 return binary(left, right, ar, no);
             }
             else{
                 left=mid;
                 return binary(left, right, ar, no);
                         }
        }
	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 (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int I() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long L() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double D() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    }
    static int gcd(int a,int b)
		{
		    if(a%b==0)
		    return b;
		    return gcd(b,a%b);
		}
	static float power(float x, int y) 
    { 
        float temp; 
        if( y == 0) 
            return 1; 
        temp = power(x, y/2);  
          
        if (y%2 == 0) 
            return temp*temp; 
        else
        { 
            if(y > 0) 
                return x * temp * temp; 
            else
                return (temp * temp) / x; 
        } 
    } 
//        static long pow(long x,long y)
//        {
//            int m=1000000007;
//            x=x%m;
//            if(y==1)
//                return x;
//            long ans=1;
//            long val=pow(x,y/2)%m;
//            ans=(val*val)%m;
//            if(y%2!=0)
//            {
//                ans=(val*x)%m;
//            }
//            return ans%m;
//        }
      static long pow(long x, long y) 
    { 
        int p = 1000000007;
        long res = 1;      
        x = x % p;  
        while (y > 0) 
        { 
            if((y & 1)==1) 
                res = (res * x) % p;
            y = y >> 1;  
            x = (x * x) % p;  
        } 
        return res; 
    } 
    static ArrayList<Integer> sieveOfEratosthenes(int n) 
    { 
        ArrayList<Integer> arr=new ArrayList<Integer>();
        boolean prime[] = new boolean[n+1]; 
        for(int i=2;i<n;i++) 
            prime[i] = true; 
          
        for(int p = 2; p*p <=n; p++) 
        { 
            if(prime[p] == true) 
            { 
                arr.add(p);
                for(int i = p*p; i <= n; i += p) 
                    prime[i] = false; 
            } 
        } 
        return arr;
    } 
}