Problem:
Score : 200 points

Problem Statement

You are given a string S consisting of lowercase English letters.
We will write down this string, starting a new line after every w letters. Print the string obtained by concatenating the letters at the beginnings of these lines from top to bottom.

Constraints

1 \leq w \leq |S| \leq 1000

S consists of lowercase English letters.

w is an integer.

Input

Input is given from Standard Input in the following format:

S
w

Output

Print the desired string in one line.

Sample Input 1

abcdefgh
3

Sample Output 1

adg

When we write down abcdefgh, starting a new line after every three letters, we get the following:

abc

def

gh

Concatenating the letters at the beginnings of these lines, we obtain adg.

Sample Input 2

lllll
1

Sample Output 2

lllll

Sample Input 3

souuundhound
2

Sample Output 3

suudon

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

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using static System.Console;
using static System.Math;

namespace AtCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var s = Read();
            var w = ReadInt();
            var ans = "";
            for (int i = 0; i < s.Count(); i+=w)
            {
                ans += s[i];
            }
            WriteLine(ans);
        }
        

        private static string Read() { return ReadLine(); }
        private static string[] Reads() { return (Read().Split()); }
        private static int ReadInt() { return int.Parse(Read()); }
        private static long ReadLong() { return long.Parse(Read()); }
        private static double ReadDouble() { return double.Parse(Read()); }
        private static int[] ReadInts() { return Array.ConvertAll(Read().Split(), int.Parse); }
        private static long[] ReadLongs() { return Array.ConvertAll(Read().Split(), long.Parse); }
        private static double[] ReadDoubles() { return Array.ConvertAll(Read().Split(), double.Parse); }

        //最大公約数
        
        public static int Gcd(int a, int b)
        {
            if (a < b)
            {
                return Gcd(b, a);
            }
            while (b != 0)
            {
                var reminder = a % b;
                a = b;
                b = reminder;
            }
            return a;
        }

        //最小公倍数
        public static int Lcm(int a, int b)
        {
            return a * b / Gcd(a, b);
        }

        //文字数を数える
        public static int CountChar(string s, char c)
        {
            return s.Length - s.Replace(c.ToString(), "").Length;
        }
    }
}