#include <stdio.h>
#include <stdbool.h>
#include <ctype.h>
#include <string.h>

enum state {TOP, ERROR};

int main(void)
{
  // initial state is outside of any tag, and not inside any elements
  // of interest
  enum state curr = TOP;

  int ch;
  while ((ch = fgetc(stdin)) != EOF)
    {
      // one case in the switch per state
      switch (curr)
	{
	case TOP:
	  // what do we do when outside any tag and we see ch?
	  break;

	// define cases for additional states you define here 
	  
	case ERROR:
	  // we can send things here as a precaution when things
	  // are in the wrong place and then keep doing nothing
	  // until the end of file
	  break;
	}
    }
}