import java.util.HashMap;

import java.util.Scanner;

public class DominatedSubArray

{

public static void main( String[] args )

{

Scanner s = new Scanner( System.in );

int t = s.nextInt();

while( t-- > 0 )

{

int n = s.nextInt();

int[] A = new int[ n ];

for( int i = 0; i < n; i++ )

A[i] = s.nextInt();

System.out.println( shortestDominatedArray( A, n ) );

}

}

private static int shortestDominatedArray( int[] A, int n )

{

if( n == 1 )

return -1;

HashMap<Integer, String> map = new HashMap<Integer, String>();

int minDist = Integer.MAX_VALUE;

for( int i = 0; i < n; i++ )

{

if( !map.containsKey( A[i] ) )

{

map.put( A[i], i + "_" + Integer.MAX_VALUE );

}

else

{

String[] value = map.get( A[i] ).split( "_" );

int index = Integer.parseInt( value[0] );

int dist = Integer.parseInt( value[1] );

if( dist > i - index )

dist = i - index;

String val = i + "_" + dist;

map.put( A[i], val );

if( dist < minDist )

minDist = dist;

}

}

if( minDist == Integer.MAX_VALUE )

minDist = -1;

else

minDist = minDist + 1;

return minDist;

}

}