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

int main(){
    int x;
    cin >> x;
    while (x--){
        int n;
        cin >> n;
        vector<int> arr(n);
        for (int i = 0; i < n; ++i)
            arr[i] = i + 1;
        for (int i = 0; i + 1 < n; i += 2) {
            swap(arr[i], arr[i + 1]);
        }
        if (n% 2 == 1) {
            swap(arr[n - 2], arr[n- 1]);
        }
        for (int i=0; i<n;++i) {
            cout << arr[i] << " ";
        }
        cout << endl;
    }
    return 0;
}