Problem:
Score : 300 points

Problem Statement

You are given an integer sequence of length n, a_1, ..., a_n.
Let us consider performing the following n operations on an empty sequence b.

The i-th operation is as follows:

Append a_i to the end of b.

Reverse the order of the elements in b.

Find the sequence b obtained after these n operations.

Constraints

1 \leq n \leq 2\times 10^5

0 \leq a_i \leq 10^9

n and a_i are integers.

Input

Input is given from Standard Input in the following format:

n
a_1 a_2 ... a_n

Output

Print n integers in a line with spaces in between.
The i-th integer should be b_i.

Sample Input 1

4
1 2 3 4

Sample Output 1

4 2 1 3

After step 1 of the first operation, b becomes: 1.

After step 2 of the first operation, b becomes: 1.

After step 1 of the second operation, b becomes: 1, 2.

After step 2 of the second operation, b becomes: 2, 1.

After step 1 of the third operation, b becomes: 2, 1, 3.

After step 2 of the third operation, b becomes: 3, 1, 2.

After step 1 of the fourth operation, b becomes: 3, 1, 2, 4.

After step 2 of the fourth operation, b becomes: 4, 2, 1, 3.

Thus, the answer is 4 2 1 3.

Sample Input 2

3
1 2 3

Sample Output 2

3 1 2

As shown above in Sample Output 1, b becomes 3, 1, 2 after step 2 of the third operation. Thus, the answer is 3 1 2.

Sample Input 3

1
1000000000

Sample Output 3

1000000000

Sample Input 4

6
0 6 7 6 7 0

Sample Output 4

0 6 6 0 7 7

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

// using System.Numerics;
using System.Runtime.CompilerServices;
using System.Diagnostics;
using ll=System.Int64;
using static Contest_A.Lib_IO;
using static Contest_A.Lib_Minifunc;



public static class Contest_A
{

	public static void Main() {
		checked{
			long n;
			Lib_IO.rm(out n);
			ll[] a;
			ra(out a);

			Deque<ll> d = new Deque<ll>();
			for (int i = 0; i < n; i++)
			{
				if(i%2==0){
					d.PushBack(a[i]);
				}else{
					d.PushFront(a[i]);
				}
			}

			List<ll> ans = new List<ll>();
			if(n%2==0){
				while(0<d.Count) ans.Add(d.PopFront());
			}else{
				while(0<d.Count) ans.Add(d.PopBack());
			}

			Lib_IO.wa(ans);
		}
	}


public class Deque<T> {
	int dx;
	T[] buf;
	int mask;

	/// <summary>
	///<see cref="Deque{T}"/> に格納されている要素の数を取得します．
	/// </summary>
	/// <remarks>この操作は計算量 O(1) で実行されます．</remarks>
	public int Count { get; private set; }
	
	/// <summary>
	/// 空であって，既定の初期容量を備えた <see cref="Deque{T}"/> クラスの新しいインスタンスを初期化します．
	/// </summary>
	public Deque() : this(8) { }
	
	/// <summary>
	/// 空であって，指定の初期容量を備えた <see cref="Deque{T}"/> クラスの新しいインスタンスを初期化します．
	/// </summary>
	/// <param name="capacity">作成したインスタンスが格納できる要素数の初期値．2 べきの値にしてください．</param>
	public Deque(int capacity) {
		int nbase = 1;  // 追加
		while((1 << nbase) < capacity) nbase++;  // 追加
		capacity = 1 << nbase;  // 追加
		Debug.Assert(capacity == (capacity & -capacity));
		mask = capacity - 1;
		buf = new T[capacity];
	}
	
	/// <summary>
	/// 指定したインデックスにある要素を取得または設定します．
	/// </summary>
	/// <param name="index">取得または設定する要素の，0-inexed での番号．</param>
	/// <returns>指定したインデックス位置にある要素</returns>
	/// <remarks>この操作は計算量 O(1) で実行されます．</remarks>
	public T this[int index] {
		get {
			Debug.Assert(0 <= index && index < Count);
			return buf[(dx + index) & mask];
		}
		set {
			Debug.Assert(0 <= index && index < Count);
			buf[(dx + index) & mask] = value;
		}
	}

	/// <summary>
	/// <see cref="Deque{T}"/> の先頭に要素を追加します．
	/// </summary>
	/// <param name="item">追加する要素</param>
	/// <remarks>この操作はならし計算量 O(1) で実行されます．</remarks>
	public void PushFront(T item) {
		if (Count == buf.Length) extend();
		dx = (dx + buf.Length - 1) & mask;
		buf[dx] = item;
		Count++;
	}

	/// <summary>
	/// <see cref="Deque{T}"/> の先頭から要素を削除し，返します．
	/// </summary>
	/// <remarks>この操作は計算量 O(1) で実行されます．</remarks>
	public T PopFront() {
		Debug.Assert(Count > 0);
		var ret = buf[dx];  // 修正
		dx = (dx + 1) & mask;  // 修正
		Count--;
		return ret;
	}

	/// <summary>
	/// <see cref="Deque{T}"/> の末尾に要素を追加します．
	/// </summary>
	/// <param name="item">追加する要素</param>
	/// <remarks>この操作はならし計算量 O(1) で実行されます．</remarks>
	public void PushBack(T item) {
		if (Count == buf.Length) extend();
		buf[(dx + Count++) & mask] = item;
	}
	
	/// <summary>
	/// <see cref="Deque{T}"/> の末尾から要素を削除し，返します．
	/// </summary>
	/// <remarks>この操作は計算量 O(1) で実行されます．</remarks>
	public T PopBack() {
		Debug.Assert(Count > 0);
		var ret = buf[(dx + --Count) & mask];
		return ret;
	}

	/// <summary>
	/// <see cref="Deque{T}"/> の末尾の要素を返します．
	/// </summary>
	/// <remarks>この操作は計算量 O(1) で実行されます．</remarks>
	public T Last() {
		Debug.Assert(Count > 0);
		return buf[(dx + Count - 1) & mask];
	}
	
	/// <summary>
	/// <see cref="Deque{T}"/> の先頭の要素を返します．
	/// </summary>
	/// <remarks>この操作は計算量 O(1) で実行されます．</remarks>
	public T First() {
		Debug.Assert(Count > 0);
		return buf[dx];
	}

	void extend() {
		var nbuf = new T[buf.Length * 2];
		for (int i = 0; i < buf.Length; i++)
			nbuf[i] = buf[(dx + i) & mask];
		mask = mask * 2 + 1;
		dx = 0;
		buf = nbuf;
	}
	
	/// <summary>
	/// デックを空にします．
	/// </summary>
	/// <remarks>この操作は O(1) で実行されます．</remarks>
	public void Clear() { Count = 0; }
	
	/// <summary>
	/// <see cref="Deque{T}"/> 内に要素が存在するかどうかを調べます．
	/// </summary>
	/// <returns>要素が存在するならば true，そうでなければ false</returns>
	/// <remarks>この操作は O(1) で実行されます．</remarks>
	public bool Any() { return Count != 0; }
	
	/// <summary>
	/// 指定した位置に要素を挿入します．
	/// </summary>
	/// <param name="item">追加したい要素</param>
	/// <param name="index">追加したい位置の 0-indexed での番号</param>
	/// <remarks>この操作は最悪計算量 O(N) で実行されます．</remarks>
	public void Insert(int index, T item) {
		Debug.Assert(0 <= index && index <= Count);
		PushFront(item);
		for (int i = 0; i < index; i++)
			this[i] = this[i + 1];
		this[index] = item;
	}
	
	/// <summary>
	/// 指定した位置にある要素を削除し，返します．
	/// </summary>
	/// <param name="index">削除したい位置の 0-indexed での番号</param>
	/// <remarks>この操作は最悪計算量 O(N) で実行されます．</remarks>
	public T RemoveAt(int index) {
		Debug.Assert(0 <= index && index < Count);
		var ret = this[index];
		for (int i = index; i > 0; i--)
			this[i] = this[i - 1];
		PopFront();
		return ret;
	}

	/// <summary>
	/// <see cref="Deque{T}"/> 内にある要素の一覧を返します．
	/// </summary>
	/// <returns><see cref="Deque{T}"/> 内にある要素の一覧</returns>
	/// <remarks>この操作は O(N) で実行されます．</remarks>
	public T[] Items {
		get {

			var ret = new T[Count];
			for (int i = 0; i < Count; i++)
				ret[i] = this[i];
			return ret;
		}
	}
}

















#region BaseModule


public static class Lib_Minifunc{
	[MethodImpl(256)] public static void swap1<T>(ref T a, ref T b) { T t = a; a = b; b = t; }
	[MethodImpl(256)] public static void swap2<T>(ref T a, ref T b) where T : IComparable { if (a.CompareTo(b)==1) swap1(ref a, ref b); }  // b の方が小さければ交換
	[MethodImpl(256)] public static bool chmin<T>(ref T a, T b) where T : IComparable { if (a.CompareTo(b)== 1) { a = b; return true; } return false; }  // b の方が小さければ a を更新
	[MethodImpl(256)] public static bool chmax<T>(ref T a, T b) where T : IComparable { if (a.CompareTo(b)==-1) { a = b; return true; } return false; }  // b の方が大きければ a を更新
	[MethodImpl(256)] public static bool inside(long i, long n) => (0<=i&&i<n);
	[MethodImpl(256)] public static bool inside(long x, long y, long w, long h) => (inside(x,w)&&inside(y,h));
	[MethodImpl(256)] public static T min<T>(params T[] a) where T : IComparable => a.Min();
	[MethodImpl(256)] public static T max<T>(params T[] a) where T : IComparable => a.Max();
	[MethodImpl(256)] public static long mod(long a, long m=MOD1) { var v = a%m; return (v<0?v+m:v); }
	[MethodImpl(256)] public static long ceiling(long a, long b) => (a%b==0?a/b:a/b+1);	// 整数商の切り上げ
	[MethodImpl(256)] public static P<T,U> initp<T,U>(T a,U b) => new P<T,U>(a,b);
	[MethodImpl(256)] public static P<T,U,V> initp<T,U,V>(T a,U b,V c) => new P<T,U,V>(a,b,c);
	[MethodImpl(256)] public static P<T,U,V,W> initp<T,U,V,W>(T a,U b,V c,W d) => new P<T,U,V,W>(a,b,c,d);
	[MethodImpl(256)] public static bool initd<T,U>(Dictionary<T,U> d, T k) { if(d.ContainsKey(k)) { return false; } else { d[k] = default(U); return true; } }
	public static T[] inita<T>(long len1) where T : new() { var m = new T[len1]; for (int i=0;i<m.Length;i++) m[i] = new T(); return m; }
	public static T[][] initm<T>(long len1,long len2,T val) where T : struct { var m = new T[len1][]; for (int i=0;i<m.Length;i++) m[i] = Enumerable.Repeat(val,(int)len2).ToArray(); return m; }
	public static T[][][] initm<T>(long len1,long len2,long len3,T val) where T : struct { var m = new T[len1][][]; for (int i=0;i<m.Length;i++) m[i] = initm(len2,len3,val); return m; }
	public const long MOD1 = 1000000007; // 10^9+7
	public const double EPS1 = 1e-8;
	public const long INF1 = 1000000000000000;  // 10^15
}

public struct P<T,U>
{
	public T A; public U B;
	public P(T a,U b) { A = a; B = b; }
	public static implicit operator KeyValuePair<T,U>(P<T,U> a) => new KeyValuePair<T,U>(a.A,a.B);
	public static implicit operator P<T,U>(KeyValuePair<T,U> a) => new P<T,U>(a.Key,a.Value);
}
public struct P<T,U,V>
{
	public T A; public U B; public V C;
	public P(T a,U b,V c) { A = a; B = b; C = c; }
}
public struct P<T,U,V,W>
{
	public T A; public U B; public V C; public W D;
	public P(T a,U b,V c,W d) { A = a; B = b; C = c; D = d; }
}

public static class Lib_IO
{
	class Prt : System.IO.StreamWriter
	{
		public override IFormatProvider FormatProvider { get { return System.Globalization.CultureInfo.InvariantCulture; } }
		public Prt(System.IO.Stream s) : base(s,new UTF8Encoding(false,true)) {}
		public Prt(System.IO.Stream s,Encoding e) : base(s,e) {}
	}
	static Prt sw = new Prt(Console.OpenStandardOutput());
	static char[] sp = new char[] {' '};
	[MethodImpl(256)] static bool eq<T,U>() => typeof(T).Equals(typeof(U));
	[MethodImpl(256)] static T ct<T,U>(U a) => (T)Convert.ChangeType(a,typeof(T));
	[MethodImpl(256)] static T cv<T>(string s) =>
		eq<T,int>()	? ct<T,int>(int.Parse(s))
	  : eq<T,long>()   ? ct<T,long>(long.Parse(s))
	  : eq<T,double>() ? ct<T,double>(double.Parse(s,System.Globalization.CultureInfo.InvariantCulture))
	  : eq<T,char>()   ? ct<T,char>(s[0])
					   : ct<T,string>(s);
	public static string[] rm<T>(out T a) {
		var z = Console.ReadLine().Split(sp,StringSplitOptions.RemoveEmptyEntries); 
		a = cv<T>(z[0]);
		return z;
	}
	public static string[] rm<T,U>(out T a,out U b) {
		var z = rm<T>(out a); 
		b = cv<U>(z[1]);
		return z;
	}
	public static string[] rm<T,U,V>(out T a,out U b,out V c) {
		var z = rm<T,U>(out a,out b); 
		c = cv<V>(z[2]);
		return z;
	}
	public static string[] rm<T,U,V,W>(out T a,out U b,out V c,out W d) {
		var z = rm<T,U,V>(out a,out b,out c); 
		d = cv<W>(z[3]);
		return z;
	}
	public static string[] rm<T,U,V,W,X>(out T a,out U b,out V c,out W d,out X e) {
		var z = rm<T,U,V,W>(out a,out b,out c,out d); 
		e = cv<X>(z[4]);
		return z;
	}
	public static string[] rm<T,U,V,W,X,Y>(out T a,out U b,out V c,out W d,out X e,out Y f) {
		var z = rm<T,U,V,W,X>(out a,out b,out c,out d,out e); 
		f = cv<Y>(z[5]);
		return z;
	}
	public static string[] ra<T>(out T[] a) {		
		var z = Console.ReadLine().Split(sp,StringSplitOptions.RemoveEmptyEntries);
		a = z.Select(cv<T>).ToArray();
		return z;
	}
	public static string[][] rl<T>(long n,out T[] a) {
		a = new T[n];
		var y = new string[n][];
		for(int i=0;i<n;i++) y[i] = rm(out a[i]);
		return y;
	}
	public static string[][] rl<T,U>(long n,out P<T,U>[] a) {
		a = new P<T,U>[n];
		var y = new string[n][];
		for(int i=0;i<n;i++) {
			T o; U p;
			y[i] = rm(out o,out p);
			a[i] = new P<T,U>(o,p);
		}
		return y;
	}
	public static string[][] rl<T,U,V>(long n,out P<T,U,V>[] a) {
		a = new P<T,U,V>[n];
		var y = new string[n][];
		for(int i=0;i<n;i++) {
			T o; U p; V q;
			y[i] = rm(out o,out p,out q);
			a[i] = new P<T,U,V>(o,p,q);
		}
		return y;
	}
	public static string[][] rl<T,U,V,W>(long n,out P<T,U,V,W>[] a) {
		a = new P<T,U,V,W>[n];
		var y = new string[n][];
		for(int i=0;i<n;i++) {
			T o; U p; V q; W r;
			y[i] = rm(out o,out p,out q,out r);
			a[i] = new P<T,U,V,W>(o,p,q,r);
		}
		return y;
	}
	public static string[][] rx<T>(long n,out T[][] a) {
		a = new T[n][];
		var y = new string[n][];
		for(int i=0;i<n;i++) y[i] = ra(out a[i]);
		return y;
	}

	static void wwp(Action act){
		sw.AutoFlush = false;
		Console.SetOut(sw);
		act();
		Console.Out.Flush();
		sw.AutoFlush = true;
		Console.SetOut(sw);
	}
	[MethodImpl(256)] static string wfm(Type t) =>t.Equals(typeof(double)) ? "{0:F10}" : "{0}";
	public static void wm(params object[] a) {
		wwp(()=>{
			for(int i=0;i<a.Length-1;i++) Console.Write(wfm(a[i].GetType())+" ",a[i]);
			Console.WriteLine(wfm(a[a.Length-1].GetType()),a[a.Length-1]);
		});
	}
	public static void wa<T>(IList<T> a) { wxa(new IList<T>[]{a}, " "); }
	public static void wl<T>(IList<T> a) {
		wwp(()=>{
			var f = wfm(typeof(T));
			foreach(T x in a) Console.WriteLine(f,x);
		});
	}
	static void wxa<T>(IList<IList<T>> a, string s) {
		wwp(()=>{
			var f = wfm(typeof(T));
			var g = f + s;
			foreach(var b in a) {
				for(int i=0;i<b.Count-1;i++) Console.Write(g,b[i]);
				Console.WriteLine(f,b[b.Count-1]);
			}
		});
	}
	public static void wx<T>(IList<IList<T>> a) { wxa(a, " "); }
	public static void wg<T>(IList<IList<T>> a) { wxa(a, ""); }
}

#endregion



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