#include <bits/stdc++.h>
#define ll long long int
#define vi vector<int>
#define vll vector<long long int>
#define MAX(a, b) ((a) > (b) ? (a) : (b))
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define ABS(x) ((x) < 0 ? -(x) : (x))
#define setpr(x, y) cout << fixed << setprecision(x) << y
#define tr(x) cout << (#x) << " = " << (x) << "\n";
using namespace std;
void solver(void);
ll MOD = 1e9 + 7;
double pi = 2 * acos(0.0);
//vector<vector<ll>> mat( n , vector<ll> (m, 0));

int main()
{
    cin.tie(NULL);
    ios_base::sync_with_stdio(false);
    int t;
    cin >> t;
    while (t--)
        solver();
}
void solver(void)
{
    //input
    ll n;
    cin >> n;
    vll v(n);
    for (ll i = 0; i < n; i++)
    {
        v[i] = i + 1;
    }
    if (n % 2 == 0)
    {

        for (ll i = 0; i < n - 1; i = i + 2)
        {
            swap(v[i], v[i + 1]);
        }
    }
    else
    {
        for (ll i = 0; i <= n - 3; i = i + 2)
        {
            swap(v[i], v[i + 1]);
        }
        swap(v[n - 2], v[n - 1]);
    }
    for (ll i = 0; i < n; i++)
    {
        cout << v[i] << " ";
    }
    cout << "\n";
}
