#include <bits/stdc++.h>
using namespace std;

string norm(const string& s) {
  string aux;
  for (char c : s)
    if (isalnum(c)) aux += tolower(c);
    else if (isspace(c)) {
      if (!aux.size() || !isspace(aux.back())) aux += c;
    }

  string ans;
  for (int i = 0; i < aux.size();) {
    while (i < aux.size() && isspace(aux[i])) ans += aux[i], ++i;
    string word;
    while (i < aux.size() && isalnum(aux[i])) word += aux[i], ++i;
    if (word.size() > 3) ans += word;
  }
  if (ans.size() && isspace(ans[0])) ans = ans.substr(1);  // it is not clear from the statement if this line should exist or not.
  return ans;
}

int main() {
  string s;
  getline(cin, s);

  cout << norm(s);

  return 0;
}