#include <bits/stdc++.h>
using namespace std;

int main() {
    ios::sync_with_stdio(0);
    cin.tie(NULL);

    int t;
    cin >> t;

    while (t--)
    {
        int n;
        cin >> n;
        
        if (n % 2)
        {
            for (int i = 1; i <= n - 3; i += 2)
                cout << i + 1 << " " << i << " ";
            
            cout << n - 1 << " " << n << " " << n - 2 << "\n";
        }
        else
        {
            for (int i = 1; i <= n; i += 2)
                cout << i + 1 << " " << i << " ";
            cout << "\n";
        }
    }

    return 0;
}