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

#define TRUE 1
#define FALSE 0
#define MAX_WORD_LENGTH 100

char wordBuffer[MAX_WORD_LENGTH];

char* readWord(FILE* fp, int retainCase)
{
        char c = 0;
        char *ptr = wordBuffer;

        while ((c = fgetc(fp))!= EOF){
                if( isalpha(c) || c == '_' ){
                        if (!retainCase){

                                c = tolower(c);
                        }
                                *ptr++ = c;
                }
                else {
                        if (ptr > wordBuffer){
                                break;
                        }
                }
        }
        if (ptr == wordBuffer){
                return NULL;
        }
        else{
                *ptr = \0;
        }
        return wordBuffer;

}

int main(int argc, char *argv[])
{
        int retainCase = FALSE;
        int i=0, flagPos=0;
        char *output=NULL;
        if (argc > 2){
                fprintf(stderr, "Usage: %s [-c]\n", argv[0]);
                return EXIT_FAILURE;
        }
        if (argc == 2){
                if ( argv[1] == "-c"){
                        retainCase = TRUE;
                        flagPos = i;
                }
                else{
                        fprintf(stderr, "Unknown argument '%s'\n", argv[1]);
                        return EXIT_FAILURE;
                }
        }
        while ((output=readWord(stdin, retainCase)) != NULL){
                printf("%s\n", output);
        }

        return EXIT_SUCCESS;
}