text: tol, strtoll - convert a string to a long integer
  #include <stdlib.h>
  long strtol(const char *restrict str, char **restrict endptr, int base);
  long long strtoll(const char *restrict str, char **restrict endptr,
  int base)
  These functions shall convert the initial portion of the string pointed to by str to a type long and long long representation, respectively. First, they decompose the input string into three parts: is stored in the object pointed to by endptr, provided that endptr is not a null pointer.
  The strtol() function.
  Upon successful completion, these functions shall return the converted value, if any. If no conversion could be performed, 0 shall be returned and errno may be set to [EINVAL].
  If the correct value is outside the range of representable values, {LONG_MIN}, {LONG_MAX}, {LLONG_MIN}, or {LLONG_MAX} shall be returned (according to the sign of the value), and errno set to [ERANGE].
  These functions shall fail if:The following sections are informative.
  None.
  None.
  None.
  None.
  isalpha() , scanf() , strt .