#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
#include <string.h>

struct stack
{
	int inf;
	stack *next;
};

stack *init_stack()
{
	return 0;
}

void push(stack *&s, int item)
{
	stack *r;
	r = new stack;
	r->inf = item;
	r->next = s;
	s = r;
}

int pop(stack *&s)
{
	stack *r = s;
	int st;
	st = r->inf;
	s = s->next;
	free(r);
	return st;
}

int peek(stack* s)
{
	return s->inf;
}

int empty_stack(stack* &s)
{
	return (s) ? 0 : 1;
}

int main()
{
	int i=0, k;
	char c;
	FILE *fin, *f1;
	fin = fopen("data.txt", "r");
	f1 = fopen("dataout.txt", "w");
	stack *head = init_stack();
	if (fin != NULL)
	{
		while (!feof(fin))
		{
			fscanf(fin, "%d", &i);
			push(head, i);
		}
		i = pop(head);
		while (!empty_stack(head))
		{
			k = pop(head);
			if (i != k)
			{
				fprintf(f1, "%d ", i);
				i = k;
			}
		}
		fprintf(f1, "%d ", i);
	}
	else printf("not today");
	system("pause");
	fcloseall();
	return 0;
}