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

/* Convert s to lower case, updating in place. */
char *str_lower(char *s)
{
        char *stmp = s;

        while (*stmp != '\0') {
                *stmp = tolower(*stmp);
                stmp++;
        }
        return s;
}

int main(int argc, char *argv[])
{
        char *oh = "Oh";
        char hello[15] = "Hello";
        char there[] = "there";
        int  idx = (argc > 2) ? atoi(argv[2]) % 5 : 1;

        printf("%s, %s %s, %s%c\n",
               oh, str_lower(hello), there,
               (argc > 1) ? argv[1] : "you",
               idx[".!?:;"]);
  
        return 0;
}