import os
import sys
from io import BytesIO, IOBase
from collections import defaultdict


def solution(arr, n):
    if n == 1:
        write(-1)
        return

    di = defaultdict(list)

    for i in range(n):
        di[arr[i]].append(i)

    res, found = float('inf'), False
    for _, indices in di.items():
        l = len(indices)
        for i in range(1, l):
            res = min(res, indices[i] - indices[i - 1] + 1)
            found = True
            if res == 2:
                write(2)
                return

    write(res if found else -1)


def main():
    for _ in range(r_int()):
        n = r_int()
        arr = r_array()
        solution(arr, n)


BUFSIZE = 8192


class FastIO(IOBase):
    newlines = 0

    def __init__(self, file):
        self._fd = file.fileno()
        self.buffer = BytesIO()
        self.writable = "x" in file.mode or "r" not in file.mode
        self.write = self.buffer.write if self.writable else None

    def read(self):
        while True:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            if not b:
                break
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines = 0
        return self.buffer.read()

    def readline(self):
        while self.newlines == 0:
            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
            self.newlines = b.count(b"\n") + (not b)
            ptr = self.buffer.tell()
            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
        self.newlines -= 1
        return self.buffer.readline()

    def flush(self):
        if self.writable:
            os.write(self._fd, self.buffer.getvalue())
            self.buffer.truncate(0), self.buffer.seek(0)


class IOWrapper(IOBase):
    def __init__(self, file):
        self.buffer = FastIO(file)
        self.flush = self.buffer.flush
        self.writable = self.buffer.writable
        self.write = lambda s: self.buffer.write(s.encode("ascii"))
        self.read = lambda: self.buffer.read().decode("ascii")
        self.readline = lambda: self.buffer.readline().decode("ascii")


sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)


def input():
    return sys.stdin.readline().rstrip("\r\n")


def write(*args, end='\n'):
    for x in args:
        sys.stdout.write(str(x) + ' ')
    sys.stdout.write(end)


def r_array():
    return [int(x) for x in input().split()]


def r_int():
    return int(input())


if __name__ == "__main__":
    main()
