#include <string.h>

char* strtok(char* restrict s, const char* restrict sep) {
  static char* p;
  if (!s && !(s = p))
    return NULL;
  s += strspn(s, sep);
  if (!*s)
    return p = 0;
  p = s + strcspn(s, sep);
  if (*p)
    *p++ = 0;
  else
    p = 0;
  return s;
}