#include <iostream>
#pragma warning(disable : 4996)
#include <string>
using namespace std;


int main()
{

	freopen("input.txt", "r", stdin);
	freopen("output.txt", "w", stdout);



	string str;

	string sentence = "";

	while (getline(cin, str)) {
		string temp;
		for (auto ch1 : str) {
			if ((ch1 >= 65) && (ch1 <= 90)) { //big chars
				ch1 += 32;
				temp += ch1;
			}
			else if ((ch1 >= 97) && (ch1 <= 122)) { //small chars
				temp += ch1;
			}
			else if ((ch1 >= 48) && (ch1 <= 57)) { //numbers
				temp += ch1;
			}
			else if (ch1 == 32) {
				if (!temp.empty()) {

					if (temp.size() > 3) {
						sentence += temp + " ";
					}
					temp = "";
				}

			}
			else if (ch1 == 10 || ch1 == 13) {
				sentence += ch1;
			}
		}

	}

	cout << sentence ;



	return 0;

}