#include<bits/stdc++.h>
using namespace std;
int main()
{
    long long n;
    cin>>n;
    long long a[n+1];
    vector<long long> v,v2;
    for(int i=1;i<=n;i++)
    {
        cin>>a[i];
        if(i%2) v.push_back(a[i]);
        else v2.push_back(a[i]);
    }
    for(int i=0;i<v.size();i++) cout<<v[i]<<" ";
    cout<<endl;
    for(int i=0;i<v2.size();i++) cout<<v2[i]<<" ";
    return 0;
}

（B3661）的法二