/*
 * ISA 563, Spring 2011
 * Copyleft by Muhammad Abdulla
 */

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

typedef enum {false, true} bool;

#define MAX 100
#define MAXLINE 32

int stack_idx = 0;

int stack[MAX];

void stack_push(int item)
{
   if ( stack_idx < MAX ) {
      stack[stack_idx++] = item;
   } else {
      fprintf(stderr, "stack is full, returning.\n");
   }
}

int  stack_pop()
{
   if ( stack_idx > 0 ) {
      return stack[--stack_idx]; 
   } else {
      fprintf(stderr, "stack is empty, returning -1.\n");
      return -1;
   }
}

bool stack_empty()
{
   return stack_idx > 0 ? 0 : 1;
}

bool stack_full()
{
   return stack_idx < MAX ? 0 : 1;
}

int main ( int argc, char *argv[] )
{
   int i;
   char line[MAXLINE];

   fprintf(stdout, "Please enter numbers to stacked:\n");

   while ( fgets(line, sizeof(line), stdin) ) {
      i = atoi(line); 

      if ( ! stack_full() ) {
         stack_push(i);
      }
   }

   while ( ! stack_empty() ) {
      fprintf(stdout, "%d\n", stack_pop());
   }

   return 0;
}