#include <string>
#include <iostream>
#include <fstream>

using namespace std;

bool isValidEmialCharacter(char c) // Check each individual character to see if it is valid for an email address
{
  bool result = false;

  if (c >='A' && c <='Z')
    result = true;
  else if (c >='a' && c <='z')
    result = true;
  else if (c >='0' && c <='9')
    result = true;
  else if ( c =='!' || c =='#' || c =='$' || c =='%' || c =='&' || c =='*' || c =='+' || c =='-' || c =='/' || c =='=' || c =='?' || c =='^' || c =='_' || c =='`' || c =='{' || c =='|' || c =='}' || c =='~' || c =='.')
    result = true;

  return result;
}

int main()
{
  string input;
  string output;
  string emptycompare = "";  // Used to compare input with default names
  ifstream fin;

  cout << "Enter input filename [default: fileContainingEmails.txt]: ";
  getline(cin, input);
  if (input.compare(emptycompare) == 0)  // If no input is supplied, the default file is opened
  {
    input = "fileContainingEmails.txt";
    fin.open(input.c_str());
  }
  else // If an input is supplied, that is opened instead
    fin.open(input.c_str());
  if (!fin.good()) throw "I/O error";

  cout << "Input file: " << input << endl;

  while (!fin.eof())
  {
    string lineFromFile;
    fin >> lineFromFile;
	fin.ignore(0, 10);
	for (int i = 0; i < lineFromFile.length(); i++)
	  if (lineFromFile[i] == '@')
	    cout << lineFromFile[i] << endl;
  }
  return 0;
}