double atof(const char *s);
    int atoi(const char *s);
    long atol(const char *s);
    double strtod(const char *s, char **endp);
    long strtol(const char *s, char **endp, int base);
    unsigned long strtoul(counst char *s, char **endp, int base);
    int rand(void);
    void srand(unsigned int seed);
    void *calloc(size_t nobj, size_t size);
    void *malloc(size_t size);
    void *realloc(void *p, size_t size);
    void free(void *p);
    void abort(void);
    void exit(int status);
    int atexit(void (*fcn)(void));
    int system(const char *s);
    char *getenv(const char *name);
    void *bsearch(const void *key, const void *base);
    void qsort(void *base, size_t n, size_t size,
	       int (*cmp)(const void *, const void *));
    int abs(int n);
    long labs(long n);
    div_t div(int num, int denom);
    ldiv_t ldiv(long num, long denom);