# ------------------- fast io --------------------
import os
import sys
from io import BytesIO, IOBase
 
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)
input = lambda: sys.stdin.readline().rstrip("\r\n")
 
# ------------------- fast io --------------------

testcases=int(input())

for j in range(testcases):
    n=int(input())
    vals=list(map(int,input().split()))
    #i have an idea, jsut find any subarray that has 2 repeating
    setty=set([])
    arr1=[]
    dict1={}
    for s in range(n):
        if not(vals[s] in setty):
            setty.add(vals[s])
            dict1[vals[s]]=[s]
        else:
            dict1[vals[s]].append(s)
    #we need the len of the values to be greater than 2
    exi=False
    for s in dict1.keys():
        if len(dict1[s])>=2:
            exi=True
            break
    if exi==False:
        print(-1)
    else:
        minlength=n+1
        for s in dict1.keys():
            val=dict1[s]
            for b in range(1,len(val)):
                length=val[b]+1-val[b-1]
                if length<minlength:
                    minlength=length
        print(minlength)