// #define LOCAL
#define _USE_MATH_DEFINES
#include <array>
#include <cassert>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <vector>
#include <queue>
#include <stack>
#include <list>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <algorithm>
#include <complex>
#include <cmath>
#include <numeric>
#include <bitset>
#include <functional>
#include <random>
#include <ctime>

using namespace std;

template <typename A, typename B>
ostream& operator <<(ostream& out, const pair<A, B>& a) {
  out << "(" << a.first << "," << a.second << ")";
  return out;
}
template <typename T, size_t N>
ostream& operator <<(ostream& out, const array<T, N>& a) {
  out << "["; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
template <typename T>
ostream& operator <<(ostream& out, const vector<T>& a) {
  out << "["; bool first = true;
  for (auto v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "]";
  return out;
}
template <typename T, class Cmp>
ostream& operator <<(ostream& out, const set<T, Cmp>& a) {
  out << "{"; bool first = true;
  for (auto& v : a) { out << (first ? "" : ", "); out << v; first = 0;} out << "}";
  return out;
}
template <typename U, typename T, class Cmp>
ostream& operator <<(ostream& out, const map<U, T, Cmp>& a) {
  out << "{"; bool first = true;
  for (auto& p : a) { out << (first ? "" : ", "); out << p.first << ":" << p.second; first = 0;} out << "}";
  return out;
}
#ifdef LOCAL
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
#else
#define trace(...) 42
#endif
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
  cerr << name << ": " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
  const char* comma = strchr(names + 1, ',');
  cerr.write(names, comma - names) << ": " << arg1 << " |";
  __f(comma + 1, args...);
}

template <class T> auto vect(const T& v, int n) { return vector<T>(n, v); }
template <class T, class... D> auto vect(const T& v, int n, D... m) {
  return vector<decltype(vect(v, m...))>(n, vect(v, m...));
}

typedef long long int64;
typedef pair<int, int> ii;
#define SZ(x) (int)((x).size())
template <typename T> static constexpr T inf = numeric_limits<T>::max() / 2;
const int MOD = 1e9 + 7;
mt19937 mrand(random_device{}());
int rnd(int x) { return mrand() % x; }

struct fast_ios {
  fast_ios() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
  };
} fast_ios_;

int main() {
  int cas;
  cin >> cas;
  while (cas--) {
    int n;
    cin >> n;
    vector<int> a(n), pos(n);
    for (int i = 0; i < n; ++i) {
      cin >> a[i];
      --a[i];
      pos[a[i]] = i;
    }
    if (n == 2) {
      if (a[0] == 0) {
        cout << 0 << '\n';
        cout << '\n';
      } else {
        cout << 1 << '\n';
        cout << 1 << '\n';
      }
      continue;
    }
    vector<int> ret;
    auto add =
      [&](int x) {
        ret.push_back(x);
        swap(pos[a[x]], pos[a[x + 1]]);
        swap(a[x], a[x + 1]);
      };
    int k = 0;
    for (int i = n - 1; i >= 0; --i) {
      trace(a, pos, ret, i);
      if (i == 2) {
        while (a[0] != 0 || a[1] != 1 || a[2] != 2) {
          add(k);
          k ^= 1;
        }
        break;
      }
      if (pos[i] == i) continue;
      while (pos[i] % 2 != k) {
        add(k);
        k ^= 1;
      }
      int j = pos[i];
      for (int t = j; t < i; ++t) {
        add(t);
        k ^= 1;
      }
    }
    cout << SZ(ret) << '\n';
    for (int i = 0; i < SZ(ret); ++i) {
      cout << ret[i] + 1 << " \n"[i + 1 == SZ(ret)];
    }
    if (SZ(ret) == 0) cout << '\n';
  }

  return 0;
}

#include <bits/stdc++.h>
// #include <atcoder/all>
// using namespace atcoder;
#define rep(i, n) for (ll i = 0; i < (ll)(n); ++i)
#define rep2(i, s, n) for (ll i = s; i < (ll)(n); i++)
#define repr(i, n) for (ll i = n; i >= 0; i--)
#define pb push_back
#define COUT(x) cout << (x) << "\n"
#define COUTF(x) cout << setprecision(15) << (x) << "\n"
#define ENDL cout << "\n"
#define DF(x) x.erase(x.begin())
#define ALL(x) x.begin(), x.end()
#define SORT(x) sort(ALL(x))
#define RSORT(x) sort(x.rbegin(), x.rend())
#define REVERSE(x) reverse(ALL(x))
#define MAX(x) *max_element(ALL(x))
#define MAXI(x) max_element(ALL(x)) - x.begin()
#define SUM(x) accumulate(ALL(x), 0ll)
#define COUNT(x, y) count(ALL(x), y);
#define ANS cout << ans << "\n"
#define YES cout << "YES\n";
#define NO cout << "NO\n";
#define Yes cout << "Yes\n";
#define No cout << "No\n";
#define init() \
  cin.tie(0);  \
  ios::sync_with_stdio(false)
#define debug(x) cerr << "[debug] " << #x << ": " << x << endl;
#define debugV(v)                       \
  cerr << "[debugV] " << #v << ":";     \
  rep(z, v.size()) cerr << " " << v[z]; \
  cerr << endl;
using namespace std;
using ll = long long;
using ld = long double;
using vll = vector<ll>;
using vvll = vector<vector<ll>>;
using mll = map<ll, ll>;
using qll = queue<ll>;
using P = pair<ll, ll>;
using vp = vector<P>;
using vs = vector<string>;

template <typename T>
inline istream& operator>>(istream& i, vector<T>& v) {
  rep(j, v.size()) i >> v[j];
  return i;
}

template <typename T1, typename T2>
inline istream& operator>>(istream& i, pair<T1, T2>& v) {
  return i >> v.first >> v.second;
}

constexpr ll INF = 0x3f3f3f3f3f3f3f3f;
constexpr ld PI = 3.141592653589793238462643383279;
ll get_digit(ll x) {
  return to_string(x).size();
}

ll gcd(ll x, ll y) {
  return y ? gcd(y, x % y) : x;
}

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

template <class T>
void chmax(T& a, const T& b) {
  if (a < b) a = b;
}

template <class T>
void chmin(T& a, const T& b) {
  if (b < a) a = b;
}

signed main() {
  init();
  ll N;
  string S;
  cin >> N >> S;
  if (S[0] != S[N - 1]) {
    COUT(1);
    return 0;
  }

  bool ok = false;
  char c = S[0];
  rep2(i, 1, N - 1) {
    if (S[i] != c and S[i + 1] != c) ok = true;
  }

  if (ok) {
    COUT(2);
  } else {
    COUT(-1);
  }

  return 0;
}