#include <bits/stdc++.h>
#pragma GCC optimize("-O3")
using namespace std;
const long long N = 1e6 + 5;
const long long MAX = 1e7 + 9;
long long binarySearch(long long arr[], long long l, long long r, long long x) {
  if (r >= l) {
    long long mid = l + (r - l) / 2;
    if (arr[mid] == x) return mid;
    if (arr[mid] > x) return binarySearch(arr, l, mid - 1, x);
    return binarySearch(arr, mid + 1, r, x);
  }
  return -1;
}
void pairsort(long long a[], long long b[], long long n) {
  pair<long long, long long> pairt[n];
  for (long long i = 0; i < n; i++) {
    pairt[i].first = a[i];
    pairt[i].second = b[i];
  }
  sort(pairt, pairt + n);
  for (long long i = 0; i < n; i++) {
    a[i] = pairt[i].first;
    b[i] = pairt[i].second;
  }
}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long isprime(long long n) {
  if (n < 2) return 0;
  if (n < 4) return 1;
  if (n % 2 == 0 or n % 3 == 0) return 0;
  for (long long i = 5; i * i <= n; i += 6)
    if (n % i == 0 or n % (i + 2) == 0) return 0;
  return 1;
}
long long C(long long n, long long r) {
  if (r > n - r) r = n - r;
  long long ans = 1;
  for (long long i = 1; i <= r; i++) {
    ans *= n - r + i;
    ans /= i;
  }
  return ans;
}
long long mod = 1e9 + 7;
long long modexpo(long long x, long long p) {
  long long res = 1;
  x = x % mod;
  while (p) {
    if (p % 2) res = res * x;
    p >>= 1;
    x = x * x % mod;
    res %= mod;
  }
  return res;
}
long long countDistinct(long long arr[], long long n) {
  sort(arr, arr + n);
  long long res = 0;
  for (long long i = 0; i < n; i++) {
    while (i < n - 1 && arr[i] == arr[i + 1]) i++;
    res++;
  }
  return res;
}
long long int2Bin(string s) {
  reverse(s.begin(), s.end());
  long long b = 1;
  long long x = 0;
  for (long long i = 0; i < s.length(); ++i) {
    if (s[i] == '1') x += b;
    b *= 2;
    ;
  }
  return x;
}
long long getSum(long long n) {
  long long sum;
  for (sum = 0; n > 0; sum += n % 10, n /= 10)
    ;
  return sum;
}
long long nex(long long i) { return (i / 10 + 1) * 10 - i; }
bool up[N];
long long a[N], ind, leave[11];
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    pair<long long, long long> a[n];
    long long i;
    for (i = 0; i < n; i++) {
      long long x;
      cin >> x;
      a[i].first = x;
      a[i].second = i;
    }
    sort(a, a + n);
    long long ans = 2 * n;
    for (i = 1; i < n; i++) {
      if (a[i].first == a[i - 1].first)
        ans = min(ans, a[i].second - a[i - 1].second + 1);
    }
    if (ans == 2 * n)
      cout << "-1\n";
    else
      cout << ans << "\n";
  }
}
