// "Conflate" two sorted integer lists.

#include <iostream>
#include <fstream>
using namespace std;

int main()
{
	ifstream  listA, listB;   // The two input files
	int  numA, numB;          // Values from the input

	// Open the first file.
	listA.open("a.dat");
	if ( !listA )
	{
		cerr << "Unable to open a.dat file\n";
		return 1;
	}

	// Open the second file.
	listB.open("b.dat");
	if ( !listB )
	{
		cerr << "Unable to open b.dat file\n";
		return 1;
	}

	// Conflate (or merge) numbers from the two input list files.
	listA >> numA;
	listB >> numB;
	while ( listA || listB )
	{
		if ( !listB || ( listA && numA < numB ) )
		{
			cout << numA << endl;
			listA >> numA;
		}
		else if ( !listA || numA > numB )
		{
			cout << numB << endl;
			listB >> numB;
		}
		else  // numA == numB
		{
			cout << numA << endl;
			listA >> numA;
			listB >> numB;
		}
	}

	// Close both input files.
	listA.close();
	listB.close();

	return 0;
}