1818B - Indivisible - CodeForces Solution

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define fn(n) for (int i = 0; i < n; i++)
#define fne(n) for (int i = 1; i <= n; i++)
#define fin(x, n) for (int i = x; i < n; i++)
#define fine(x, n) for (int i = x; i <= n; i++)
#define endl "\n"
#define pb push_back
#define msdfan                        \
    ios_base::sync_with_stdio(false); \
    cin.tie(NULL);

void solve()
{
  int n;
  cin>>n;
  
  if(n==1) 
  {
      cout<<1<<endl;
      return;
  }
  if(n%2!=0) 
  {
      cout<<"-1"<<endl;
      return;
  }
  vector<int> v(n+1);
  for(int i=1;i<=n;i++)
  {
      v[i]=i;
  }
  for(int i=1;i<=n;i=i+2)
  {
      swap(v[i],v[i+1]);
  }
  for(int i=1;i<=n;i++)
  {
      cout<<v[i]<<" ";
  }
  cout<<endl;
}


int main()
{
    msdfan;
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    ll t1 = 1;
    cin >> t1;
    while (t1--)
    {
        solve();
    }
    return 0;
}