import sys
from functools import lru_cache, cmp_to_key
from heapq import merge, heapify, heappop, heappush
from math import *
from collections import defaultdict as dd, deque, Counter as C
from itertools import combinations as comb, permutations as perm
from bisect import bisect_left as bl, bisect_right as br, bisect
from time import perf_counter
from fractions import Fraction
# sys.setrecursionlimit(int(pow(10, 2)))
# sys.stdin = open("input.txt", "r")
# sys.stdout = open("output.txt", "w")
mod = int(pow(10, 9) + 7)
mod2 = 998244353
def data(): return sys.stdin.readline().strip()
def out(*var, end="\n"): sys.stdout.write(' '.join(map(str, var))+end)
def l(): return list(sp())
def sl(): return list(ssp())
def sp(): return map(int, data().split())
def ssp(): return map(str, data().split())
def l1d(n, val=0): return [val for i in range(n)]
def l2d(n, m, val=0): return [l1d(n, val) for j in range(m)]


# @lru_cache(None)




for i in range(l()[0]):
    n=l()[0]
    A=l()
    if(n<2 or len(A)==len(set(A))):
        print(-1)
        continue
    d={}
    for i in range(n):
        if(A[i] not in d):
            d[A[i]]=[]
        d[A[i]].append(i)
    m=n
    for ks in d:
        if(len(d[ks])==1):
            continue
        for i in range(1,len(d[ks])):
            curr=d[ks][i]-d[ks][i-1]
            m=min(m,curr)
    print(m+1)


