#include <iostream>
using namespace std;
int main() {
    int T;
    cin >> T;
    while (T--) {
        int N;
        cin >> N;
        if (N % 2 == 0) {
            for (int i = 1; i <= N; i += 2) {
                cout << i + 1 << " " << i << " ";
            }
        } else {
            cout << "2 3 1 ";
            for (int i = 4; i <= N; i += 2) {
                if (i + 1 <= N)
                    cout << i + 1 << " " << i << " ";
                else
                    cout << i << " ";
            }
        }
        cout << endl;
    }
    return 0;
}