#include <bits/stdc++.h>   using namespace std;   long long gcd(long long a, long long b) {     if (b == 0) return a;     return gcd(b, a % b);   }   long long a[505], ar[505], num[505], b[505];   bool used[505];   signed main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     long long t;     cin >> t;     while (t--) {       long long n;       cin >> n;       vector<long long> ans;       memset(num, 0, sizeof(num));       memset(used, 0, sizeof(used));       bool swi = false;       long long swa1, swa2;       for (long long i = 0; i < n; i++) cin >> ar[i];       for (long long i = 0; i < n; i++) {         if (num[ar[i]]) {           swi = true;           swa1 = num[ar[i]] - 1, swa2 = i;           break;         }         num[ar[i]] = i + 1;       }       for (long long i = 0; i < n; i++) {         long long p, mi = 501;         for (long long j = 0; j < n; j++)           if (!used[j] && ar[j] < mi) mi = ar[j], p = j;         a[p] = i + 1;         b[p] = i + 1;         used[p] = true;       }       long long N = n;       while (n > 3) {         long long p, ma = 0;         for (long long i = 0; i < n; i++)           if (a[i] > ma) ma = a[i], p = i;         while (p < n - 3) {           ans.push_back(p + 1);           long long tem = a[p + 2];           a[p + 2] = a[p + 1];           a[p + 1] = a[p];           a[p] = tem;           p++;         }         while (p < n - 1) {           ans.push_back(n - 2);           long long tem = a[n - 1];           a[n - 1] = a[n - 2];           a[n - 2] = a[n - 3];           a[n - 3] = tem;           p++;         }         n--;       }       bool tag = false;       for (long long i = 0; i < 3; i++) {         if (a[0] <= a[1] && a[1] <= a[2]) {           tag = true;           break;         }         ans.push_back(1);         long long tem = a[2];         a[2] = a[1];         a[1] = a[0];         a[0] = tem;       }       if (tag) {         cout << ((long long)ans.size()) <<   n ;         for (long long i : ans) cout << i <<    ;         cout <<   n ;         continue;       }       if (!swi) {         cout <<  -1  <<   n ;         continue;       }       ans.clear();       n = N;       swap(b[swa1], b[swa2]);       for (long long i = 0; i < n; i++) a[i] = b[i];       while (n > 3) {         long long p, ma = 0;         for (long long i = 0; i < n; i++)           if (a[i] > ma) ma = a[i], p = i;         while (p < n - 3) {           ans.push_back(p + 1);           long long tem = a[p + 2];           a[p + 2] = a[p + 1];           a[p + 1] = a[p];           a[p] = tem;           p++;         }         while (p < n - 1) {           ans.push_back(n - 2);           long long tem = a[n - 1];           a[n - 1] = a[n - 2];           a[n - 2] = a[n - 3];           a[n - 3] = tem;           p++;         }         n--;       }       for (long long i = 0; i < 3; i++) {         if (a[0] <= a[1] && a[1] <= a[2]) {           tag = true;           break;         }         ans.push_back(1);         long long tem = a[2];         a[2] = a[1];         a[1] = a[0];         a[0] = tem;       }       if (tag) {         cout << ((long long)ans.size()) <<   n ;         for (long long i : ans) cout << i <<    ;         cout <<   n ;       } else         cout <<  -1  <<   n ;     }     return 0;   }