#include <stdio.h>

#define TRUE 1
#define FALSE 0

typedef int BOOLEAN;
typedef int ETYPE;

typedef struct NODE *TREE;
struct NODE {
	ETYPE element;
	TREE leftChild, rightChild;
};

BOOLEAN lookup(ETYPE x, TREE T)
{
	if (T == NULL)
		return FALSE;
	else if (x == T->element)
		return TRUE;
	else if (x < T->element)
		return lookup(x, T->leftChild);
	else /* x must be > T->element */
		return lookup(x, T->rightChild);
}