/* package codechef; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
public class Codechef{
	public static void main (String[] args) throws java.lang.Exception{
		Scanner scn = new Scanner(System.in);
		int t = scn.nextInt();
		while(t-->0){
		    int n = scn.nextInt();
		    int[]arr = new int[n];
		    int[]pos = new int[n+1];
		    Arrays.fill(pos,-1);
		    for(int i=0;i<n;i++){
		        arr[i] = scn.nextInt();
		    }
		    int ans = n+1;
		    for(int i=0;i<n;i++){
		        if(pos[arr[i]]!=-1){
		            ans = Math.min(ans,i - pos[arr[i]]+1);
		        }
		        pos[arr[i]] = i;
		    }
		    System.out.println(ans==n+1?-1:ans);
		}
	}
}
