codeforces 233 A solution in cpp

 

codeforces 233 A solution in cpp

by ujjal roy

#include<bits/stdc++.h>

using namespace std;

main()

{

    int n;

    cin>>n;

    if(n%2==1) cout<<"-1"<<endl;

    else

    {

        for(int i=1;i<n;i=i+2)

        {

            cout<<i+1<<" "<<i<<" ";

        }

        cout<<endl;

    }

    return 0;

}