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

using namespace std;

int main() {
	const string str("atgctgttg");
	const int n = 5; // Assumed positive number smaller than str.size()
	const int n1 = n - 1;
	vector<string> result(str.size() - n1);

	transform(str.cbegin(), str.cend() - n1, result.begin(), [n](const auto& i) {return string(&i, n);});

	for (auto& i : result) {
		cout << i << endl;
	}
}