#include <bits/stdc++.h>
using namespace std;
int main(){
  int t; cin >> t;
  while (t--) {
    int n, odd = 0; cin >> n;
    if (n & 1) odd = 1, n -= 3;
    for (int i = 1; i <= n; i += 2) cout << i + 1 << " " << i << " ";
    if (odd) cout << n + 2 << " " << n + 3 << " " << n + 1 << " ";
    cout << endl;
  }
}