Problem:
Score : 200 points

Problem Statement

You are given a string s consisting of lowercase English letters. Extract all the characters in the odd-indexed positions and print the string obtained by concatenating them. Here, the leftmost character is assigned the index 1.

Constraints

Each character in s is a lowercase English letter.

1≤|s|≤10^5

Input

The input is given from Standard Input in the following format:

s

Output

Print the string obtained by concatenating all the characters in the odd-numbered positions.

Sample Input 1

atcoder

Sample Output 1

acdr

Extract the first character a, the third character c, the fifth character d and the seventh character r to obtain acdr.

Sample Input 2

aaaa

Sample Output 2

aa

Sample Input 3

z

Sample Output 3

z

Sample Input 4

fukuokayamaguchi

Sample Output 4

fkoaaauh

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

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

namespace ConsoleApp1
{
    public static class MyExtensions
    {
        public static string Slice(this string str, int start = 0, int stop = 0)
        {
            if (start > str.Length || stop > str.Length || start < 0 || stop < 0)
                return "";

            if (stop == 0) stop = str.Length;
            return str.Substring(start, stop - start);
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            B();
        }

        static void B()
        {
            var s = Read();
            foreach (var i in Range(1, s.Length + 1).Where(x => x % 2 != 0))
            {
                Console.Write(s[i-1]);
            }
        }

        public static IEnumerable<int> Range(int start, int stop)
        {
            if (start < 0 || stop < 0 || start > stop || (start <= 0 && stop <= 0))
                return new List<int>();

            return Enumerable.Range(start, stop - start);
        }

        public static bool IsDigit(string str)
        {
            var i = 0;
            return int.TryParse(str, out i);
        }

        public static int DigitsSum(long num)
        {
            return num.ToString().Select(x => x.ToString()).Sum(int.Parse);
        }

        public static int[] ToIntArray(string str)
        {
            return str.Select(x => x.ToString()).Select(int.Parse).ToArray();
        }

        public static string Read()
        {
            return Console.ReadLine();
        }

        public static int ReadInt()
        {
            return int.Parse(Read());
        }

        public static long ReadLong()
        {
            return long.Parse(Read());
        }

        public static IList<string> ReadSplit()
        {
            return Read().Split().ToList();
        }

        public static IList<int> ReadSplitInt()
        {
            return Read().Split().Select(int.Parse).ToList();
        }
    }
}