#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 {
            
             
                
                for (int i = 1; i <= n - 3; i += 2) {
                    
                    cout << i + 1 << " " << i << " ";
                    
                }
                
                cout << n - 1 << " " << n << " " << n - 2;
            
            
        }
        
        cout << endl;
    }

    return 0;
}