#include <iostream>
#include <iomanip>
#include <fstream>
#include <sstream>
#include <string>
#include <vector>

using namespace std;

struct inputsystem
{ string line;
  int pos, len, linenumber, numerrors;
  istream * file;
  bool dontread;

  static const char control_d = 'D' - 64;

  void clear()
  { line = "";
    pos = 0;
    len = 0;
    numerrors = 0;
    linenumber = 0;
    dontread = false;
    file = & cin; }

  void open(istream & f)
  { file = & f; }

  void close()
  { if (file != & cin)
      ((ifstream *)file)->close(); }

  inputsystem(istream & f)
  { clear();
    open(f); }

  inputsystem()
  { clear(); }  

  char get()
  { while (true)
    { if (pos < 0)
      { pos += 1;
        return ' '; }
      else if (pos == len)
       { pos += 1;
         return ' '; }
      else if (pos > len)
      { getline(* file, line);
        if (file->fail())
          return control_d;
        pos = 0;
        len = line.length();
        linenumber += 1; 
        continue; }
      char c = line[pos];
      pos += 1;
      return c; } }

  void unget()
  { pos -= 1; }

  void unget(char c)
  { pos -= 1;
    if (pos >= 0)
      line[pos] = c; }

  void error(string message, string detail = "")
  { cout << "Line " << linenumber << " Error " << message << detail << "\n";
    cout << line << "\n";
    numerrors += 1;
    if (numerrors >= 10)
    { cout << "Too many errors, giving up.\n";
      exit(1); } } };

int main(int argc, char * argv[])
{ ifstream fi;
  inputsystem in;
  if (argc > 1)
  { fi.open(argv[1]);
    if (fi.fail())
    { cout << "Can't open \"" << argv[1] << "\"\n";
      exit(1); }
    in.open(fi); }
  while (true)
  { char c = in.get();
    if (c == in.control_d)
    { cout << "end of file\n";
      break; }
    cout << "got '" << c << "'\n";
    if (c == '*')
      in.error("multiplication forbidden!\n");
    else if (c == 'i')
    { cout << "unget four times\n";
      in.unget('I');
      in.unget();
      in.unget();
      in.unget(); } }
  in.close();
  cout << "The End.\n"; }