rt，记录

#include<bits/stdc++.h>
using namespace std ;
typedef long long ll ;
const int N=1000005 ;
int a[N] ;

int main(){
	int n ;
	cin >> n ;
	for (int i=1 ; i<=(n/2) ; i++){
		a[i]=a[n-i+1]=i*2-1 ;
		a[i+n]=a[n*2-i]=i*2 ;
	} 
	for (int i=1 ; i<=(n*2) ; i++){
		if (!a[i]) cout << n << " " ; 
		else cout << a[i] << " " ; 
	}
	return 0 ;
}