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

int main() {

    int t;
    cin>>t;

    while(t--)
    {
        int n;
        cin>>n;

        if(n%2==1)
        {
            for(int i=1;i<=n-3;i+=2) cout<<i+1<<" "<<i<<" ";
            cout<<n-1<<" "<<n<<" "<<n-2;
        }
        else
        {
            for(int i=1;i<=n;i+=2) cout<<i+1<<" "<<i<<" ";
        }
        cout<<"\n";
    }
    
    return 0;
}