# -*- coding: utf-8 -*-

import sys
from collections import defaultdict

def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for j in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for j in range(c)] for j in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 18
MOD = 10 ** 9 + 7

ans = []
for _ in range(INT()):
    N = INT()
    A = LIST()
    d = defaultdict(lambda: -INF)
    mn = INF
    for i, a in enumerate(A):
        mn = min(mn, i - d[a] + 1)
        d[a] = i
    if mn == INF:
        ans.append(str(-1))
    else:
        ans.append(str(mn))
print('\n'.join(ans))
