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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <cmath>

using namespace std;

#define REP(i,n) for (int i=0;i<(n);++i)
#define REP2(i,n) for (int i=0;i<=(n);++i)
#define REP3(i,n) for (int i=1;i<=(n);++i)

static const int MAXN = 1001;
static const int MAXM = 1001;
static const int INF = 1e5;

int main() {

	string S;
	int w;
	cin >> S >> w;
	
	int index;
	index = 0;
	while (true) {
		cout << S[index];
		index += w;
		if (index >= S.length()) {
			break;
		}
	}
	cout << endl;



	//cout << "out" << endl;

	//int end;
	//cin >> end;

	return 0;
}