#include <bits/stdc++.h>
using namespace std;
int main() {
int n;
cin >> n;
vector<int> v,p;
if(n%2==0)
{
for(int i=0;i<n;i++)
{
if((i+1)%2==0)
{
cout << i+1 << " ";
}
else cout << i+1 << " ";
}
cout << endl;
}
else
{
cout << "impossible'" << endl;
}
return 0;
}
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