/*
Program: WORDS
Author : Kim Moser
Date   : 30 November, 1990
System : IBM PC / Borland Turbo C 2.0
Descrip: Parses words from stdin to stdout

Usage  : WORDS
*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static char *words[16000];
static int wordindex=0;

static int hasword(char *s);
static int hasword(char *s)
{
	int i;

	if (wordindex == 0) return 0;

	for (i=wordindex; (i>wordindex-500) && i>=0; i--) {
		if (!strcmp(words[i], s)) return (1);
	}
	return (0);
}

void usage(void)
{
	fprintf(stderr, "usage: WORDS <word_len>\n");
	exit(-1);
}

void main(int argc, char **argv)
{
	char s[512];
	int i;
	int len;

	if (argc < 2) usage();
	if ((len = atoi(argv[1])) == 0) usage();

	while (1) {
		if (gets(s) == NULL) break;
		if (!s[0]) continue;
		if (strlen(s) != len) continue;

		if (hasword(s)) {
			fputc('x', stderr);
		} else {
			fputc('.', stderr);
			if ((words[wordindex++] = strdup(s)) == NULL) {
				fprintf(stderr, "strdup() failed.\n");
				exit(-1);
			}
		}
	}

	fprintf(stderr, "\n");

	for (i=0; i<wordindex; i++) {
		printf("%s\n", words[i]);
	}
}