--- /dev/null
+#if !defined( COMMON_H )
+#define COMMON_H
+
+#define MAX(a, b) ({ typeof(a) _a = a; typeof(b) _b = b; _a > _b? _a : _b; })
+#define MIN(a, b) ({ typeof(a) _a = a; typeof(b) _b = b; _a < _b? _a : _b; })
+
+#endif // !defined( COMMON_H )