t=int(input())
count=210
for i in range(t):
    n=int(input())
    arr=list(map(int,input().split()))
    if len(arr)==1:
        print(-1)
    elif len(arr)==2:
        if arr[0]==arr[1]:
            print(2)
        else:
            print(-1)
    else:
        i = 0
        j = n-1
        while i<n-1 and j>i:
            if arr[i:j+1].count(arr[i])!=0:
                if arr[j] == arr[i]:
                    if len(set(arr[i:j])) == j - i:
                        count = min(count, j + 1 - i)
                        j -= 1
                    else:
                        j -= 1
                else:
                    j -= 1
                if j == i:
                    j = n - 1
                    i += 1
            else:
                i+=1
        print(count)
