#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <string>
//#include <cmath>
//#include <climits>
//#include <algorithm>

using namespace std;

int main() {

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


    string s, temp_s;
    getline(cin, s);
    int length = s.length(), k = 0;
    string *arr = new string[length];

    if (!isspace(s[length - 1]))
        s += " ";

    for (char c : s) {

        if (isalpha(c) || isdigit(c)) {
            c = tolower(c);
            temp_s += c;
        }

        if (isspace(c)) {
            if (temp_s.length() > 3) {
                arr[k++] = temp_s;
            }
            temp_s = "";
        }
    }

    for (int i = 0; i < k; i++) {
        if (i != k - 1)
            cout << arr[i] << " ";
        else
            cout << arr[i];

    }


    return 0;
}