#include <iostream.h>
#include <iomanip.h>
#include <stl.h>
#include <string.h>
#include <ctype.h>
#include <string>

struct word_counts {
	char word [30];
	int count;
	int len;
};

vector<struct word_counts> words [26];

void
add (char *s);

int 
main (void)
{
	char s[100], *ptr;
	int i, j;
	vector<string> tmp;

	while (cin.getline (s, 100)) {
		for (i = 0; i < strlen (s); i++)
			s[i] = tolower (s[i]);

		ptr = strtok (s, " ,!?.");

		while (ptr) {
			add (ptr);
			ptr = strtok (NULL, " ,!?.");
		}
	}


	for (i = 0; i < 26; i++) {
		for (j = 0; j < words [i].size (); j++) {
			if (words [i][j].count > 1) {
				tmp.push_back (words [i][j].word);
//				cout << words [i][j].word 
//				<< " (" << words [i][j].count
//					<< ")"<<endl;
			}
		}

		sort (tmp.begin (), tmp.end ());

		for (j = 0; j < tmp.size (); j++)
			cout << tmp [j] << endl;

		tmp.resize (0);
	}

	return 0;
}

void
add (char *s)
{
	int i, w, len, f;
	struct word_counts wc;

	len = strlen (s);

	if (len == 0)
		return;

	w = s [0] - 'a';
	f = 0;

	for (i = 0; i < words [w].size (); i++) {
		if (len == words [w][i].len && !strcmp (s, words [w][i].word)){
			f = 1;
			words [w][i].count++;
		}
	}

	if (!f) {
		strcpy (wc.word, s);
		wc.count = 1;
		wc.len = len;
		words [w].push_back (wc);
	}
}