extern int fprintf(FILE *fp, const char *format, ...);
extern int vfprintf(FILE *fp, const char *format, va_list args);
+// scanf
+extern int scanf(const char *format, ...);
+extern int fscanf(FILE *stream, const char *format, ...);
+extern int sscanf(const char *str, const char *format, ...);
+extern int vscanf(const char *format, va_list ap);
+extern int vsscanf(const char *str, const char *format, va_list ap);
+extern int vfscanf(FILE *stream, const char *format, va_list ap);
+
extern FILE *stdin;
extern FILE *stdout;
extern FILE *stderr;