#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <algorithm>

template < class iter > void
view (iter b, iter e)
{
  iter it;
  for (it = b; it != e; it++) {
    cout << *it << " ";
  }
  cout << "\n";
}

#define BE(v) v.begin(), v.end()

void
twice (int &a)
{
  a = a * 2;
}

main ()
{
  ifstream data ("data.txt");
  vector < int >v;
  copy (istream_iterator < int >(data),	// which file
	istream_iterator < int >(),	// until the end
	back_inserter (v)	// put it into v
    );
  for_each (BE (v), twice);
  copy (BE (v), ostream_iterator < int >(cout, "\n"));
}