#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
// #define int long long
const int MOD = 1000000007;
#define sz(x) (ll)(x).size()
#define rd ({ll x; cin >> x; x; })
#define dbg(x) cerr << "[" #x "]  " << (x) << "\n"
// #define errv(x) {cerr << "["#x"]  ["; for (const auto& ___ : (x)) cerr << ___ << ", "; cerr << "]\n";}
// #define cerr if(0)cerr
#define xx first
#define yy second
mt19937 rnd(std::chrono::high_resolution_clock::now().time_since_epoch().count());
/*_________________________________________________________________________________________________________________________*/

void Solve()
{
    ll n;
    cin >> n;
    if (n % 2 == 0) {
        for (ll i = 1; i <= n; i += 2)
            cout << i + 1 << " " << i << " ";
        cout << "\n";
    } else {
        for (ll i = 1; i + 1 <= n - 3; i += 2)
            cout << i + 1 << " " << i << " ";
        cout << n - 1 << " " << n << " " << n - 2 << " ";
        cout << "\n";
    }
}

int32_t main()
{
    ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int t = 1;
    cin >> t;
    for (int i = 1; i <= t; i++) {
        // cout << "Case #" << i << ": "; // cout << "Case " << i << ": ";
        Solve();
    }
    return 0;
}
// Coded by Tahsin Arafat (@TahsinArafat)