#include <iostream>
#include <vector>
using namespace std;

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

int main() {
    int t;
    cin >> t;
    while (t--) {
        solve();
    }
    return 0;
}