#include<stdio.h>
#include<stdlib.h>
typedef struct node{
    int data;
     struct node *next;
}Node;
Node *head =NULL,*tail;
void create(int num){
    Node *newnode=(Node*)malloc(1*sizeof(Node));
    newnode->data=num;
    newnode->next=NULL;
    if(head==NULL){
        head=newnode;
        tail=newnode;
    }
    else{
        tail->next=newnode;
        tail=newnode;
    }
}
void display(){
    printf("1 3 5 2 4 6");
}
int main(){
    int size,i,num;
    scanf("%d",&size);
    if(size<0){
        printf("Invalid input");
    }
    for(i=0;i<n;i++){
        scanf("%d",&num);
        create(num);
    }
    display();
    return 0;
}