233A codeforces solution.cpp

#pragma GCC optimize("ofsat")
#pragma GCC  target("avx,avx2,fma")
 
#include<bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//using namespace __gnu_pbds;
using namespace std;
 
 
#define ui              unsigned int
#define ll              long long int
#define ld              long double
#define ull             unsigned long long int
 
 
#define ff              first
#define ss              second
#define pb              push_back
#define mp              make_pair
 
 
#define pii             pair<int,int>
#define vi              vector<int>
#define mii             map<int,int>
#define pqb             priority_queue<int>
#define pqs             priority_queue<int,vi,greater<int> > //read??
 
 
#define setbits(x)      __builtin_popcountll(x) //return total setbit
#define zrobits(x)      __builtin_ctzll(x)		//return total 0 until 1 found
#define ps(x,y)         fixed<<setprecision(y)<<x
#define mk(arr,n,type)  type *arr=new type[n];
#define sz(x)           (int)x.size()
#define w(x)            int x; cin>>x; while(x--)
 
 
#define arrsort(ar,n)   sort(ar,ar+n);
#define vsort(v)        sort(v.begin(),v.end())
#define vrev(v)         reverse(v.begin(),v.end())
#define arrev(ar,n)     reverse(ar,ar+n)
 
 
#define Fo(i,k,n) 		for(i=k;k<n?i<n:i>n;k<n?i+=1:i-=1)
#define deb(x) 			cout << #x << "=" << x << endl
#define deb2(x, y) 		cout << #x << "=" << x << "," << #y << "=" << y << endl
#define iter(it, a) 	for(auto it = a.begin(); it != a.end(); it++)
#define for0(i,n)       for(ll i=0;i<n;i++)
 
 
 
#define fast 		    ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0)
 
 
#define PI              acos(-1.0)
#define EPS             1e-12
 
 
const ll 				inf = 1000000000;
const ll 				mod = 1000000000 + 7;
 
 
// int dx4[] = { 0, 0, -1, +1 };                     int dy4[] = { +1, -1, 0, 0 };
// int dx8[] = { 1, 1, 0, -1, -1, -1, 0, 1, 0 };     int dy8[] = { 0, 1, 1, 1, 0, -1, -1, -1, 0 };
 
 
 
// template<typename... T>
// void read(T&... args)
// {
// 	((cin >> args), ...);
// }
 
 
// template<typename... T>
// void write(T&&... args)
// {
// 	((cout << args <<" "), ...);
// }
 
// mt19937                 rng(chrono::steady_clock::now().time_since_epoch().count());
 
// typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
 
 
int main()
{
	#ifndef ONLINE_JUDGE
	    freopen("input.txt", "r", stdin); //No need to comment out
	    freopen("output.txt", "w", stdout);
	#endif
    fast;
    //-------------------- Bismillah  -------------> 
 
    int n;
    cin>>n;
    vector<int>v;
    if(n==1) {cout<<-1<<endl; return 0;}
    for0(i, n) v.pb(i+1);
    if(n%2==0)
    {
    	for(int i=0;i<sz(v)-1;i+=2)
	    {
	    	swap(v[i],v[i+1]);
	    }
    	for0(i, n) cout<<v[i]<<" ";
 
    }
    else
    {
    	cout<<-1<<endl;
    }
    cout<<endl;
 
 
    return 0;
}