#include <bits/stdc++.h>
#define  endl        '\n'
typedef long long ll;
using namespace std;

mt19937 mt_rand(chrono::high_resolution_clock::now().time_since_epoch().count());

const int mod = 1e9 + 7;
const int N = 5e5 + 6;

void Solve() {

    int n;
    cin >> n;
    int a[n];
    for (int i = 0 ; i < n ; i++) a[i] = i + 1;

    for (int i = 1 ; i < n ; i+=2) {
        swap(a[i], a[i - 1]);
    }

    if(n%2)
        swap(a[n - 1], a[n - 2]);
    for (auto i : a)
        cout << i << " ";
    cout << endl;

}

int main() {

    ios::sync_with_stdio(false);
    cin.tie(0);

    //freopen("input.in", "r", stdin);
    //freopen("output.out", "w", stdout);
    int tt = 1, testcase = 1;

    cin >> tt;

    while (tt--) {

        //cout<<"Case "<<testcase++<<": ";

        Solve();
    }
    return 0;
}