#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <stdlib.h>

typedef struct node_tree
{
	int key;
	struct node_tree *l, *r;
}node;

node * add(node *tree, int k)
{
	node * nodeadd = (node*)malloc(sizeof(node));
	if (nodeadd)
	{
		nodeadd->key = k;
		nodeadd->l = NULL;
		nodeadd->r = NULL;
	}
	else
	{
		printf("no memory");
	}
	if (!tree)
	{
		tree = nodeadd;
		return 0;
	}
	node * t = tree;
	do
	{
		if (k <= t->key)
		{
			if (t->l) {
				t = t->l;
			}
			else
			{
				t->l = nodeadd;
				return tree;
			}
		}
		else
		{
			if (t->r)
			{
				t = t->r;
			}
			else
			{
				t->r = nodeadd;
				return tree;
			}
		}

	} while (t);

}

int preorder(node * tree, FILE * fo)
{
	//fo = fopen("output.txt", "w");
	node * temp = tree;
	if (temp)
	{
		fprintf(fo,"%d",temp->key);
		preorder(temp->l, fo);
		preorder(temp->r, fo);
	}
}

void main()
{
	node *tree = NULL;
	int k = 0;
	FILE *fi = fopen("input.txt", "r");
		while (!feof(fi))
		{
			fscanf(fi, "%d", &k);
			tree = add(tree, k);
		}
	fclose(fi);
	FILE *fo = fopen("output.txt", "r");
	preorder(tree,fo);
	fclose(fo);

	system("pause");
}