1669B_Tripple.cpp

// Haloom
#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<vl> vvl;
typedef pair<int, int> pii;
typedef pair<double, double> pdd;
typedef pair<ll, ll> pll;
typedef vector<pii> vii;
typedef vector<pll> vll;
typedef double dl;

#define endl '\n'
#define PB push_back
#define F first
#define S second
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define sz(x) (int)x.size()

const double PI = acos(-1);
const double eps = 1e-9;
const int inf = 2000000000;
const ll infLL = 9000000000000000000;
#define MOD 1000000007

#define mem(a, b) memset(a, b, sizeof(a))
#define sqr(a) ((a) * (a))

#define optimize()              \
  ios_base::sync_with_stdio(0); \
  cin.tie(0);                   \
  cout.tie(0);
#define fraction()              \
  cout.unsetf(ios::floatfield); \
  cout.precision(10);           \
  cout.setf(ios::fixed, ios::floatfield);
#define file()                      \
  freopen("input.txt", "r", stdin); \
  freopen("output.txt", "w", stdout);

#define dbg(args...)        \
  do                        \
  {                         \
    cerr << #args << " : "; \
    debug(args);            \
  } while (0)
void debug()
{
  cerr << endl;
}
template <typename T, typename... hello>
void debug(T arg, const hello &...rest)
{
  cerr << arg << ' ';
  debug(rest...);
}

ll gcd(ll a, ll b)
{
  return __gcd(a, b);
}
ll lcm(ll a, ll b)
{
  return a * (b / gcd(a, b));
}

int diff(int a, int b)
{
  return b - a;
}

bool check_palindrome(string s)
{
  string a = s;
  reverse(a.begin(), a.end());
  if (s == a)
  {
    return true;
  }
  else
  {
    return false;
  }
}

bool check_square(int n)
{
  int s = sqrt(n);
  return s * s == n;
}

bool check_cube(int n)
{
  int s = round(cbrt(n));
  return s * s * s == n;
}

bool check_prime(int n)
{
  if (n == 1)
  {
    return false;
  }
  for (int i = 2; i * i <= n; i++)
  {
    if (n % i == 0)
    {
      return false;
    }
  }
  return true;
}

bool isFeasible(const vector<long long> &X, double meetingPoint)
{
  double maxDistance = 0;
  for (long long xi : X)
  {
    maxDistance = max(maxDistance, abs(xi - meetingPoint));
  }
  return maxDistance <= meetingPoint;
}

int sum_d(int n)
{
  int sum = 0;
  while (n > 0)
  {
    sum += n % 10;
    n /= 10;
  }
  return sum;
}

int main()
{
  optimize();

  int t;
  cin >> t;
  while (t--)
  {
    int n;
    cin >> n;

    vector<int> a(n);
    unordered_map<int, int> counts;

    for (int i = 0; i < n; i++)
    {
      cin >> a[i];
      counts[a[i]]++;
    }

    int ans = -1;
    for (int i = 0; i < n; i++)
    {
      if (counts[a[i]] >= 3)
      {
        ans = a[i];
        break;
      }
    }

    cout << ans << endl;
  }
  return 0;
}