import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class Main {

	public static void main(String[] args) throws FileNotFoundException, IOException {

		try (BufferedReader readMestre = new BufferedReader(new FileReader("mestre.txt"));
			 BufferedReader readAltes = new BufferedReader(new FileReader("altes.txt"));
			 BufferedWriter writeAux = new BufferedWriter(new FileWriter("auxiliar.txt", true)))
		{
			String linMestre = readMestre.readLine();
			String linAltes = readAltes.readLine();

			do {
				if (Integer.valueOf(linMestre) <= Integer.valueOf(linAltes)) {
					writeAux.write(linMestre);
					linMestre = readMestre.readLine();
				} else {
					writeAux.write(linAltes);
					linAltes = readAltes.readLine();
				}
				writeAux.newLine();
			} while (linMestre != null && linAltes != null);

			if (linMestre == null) acabar(readAltes, writeAux); else acabar(readMestre, writeAux);
		}

		renombrar();

		System.out.println("Fin del programa");
	}

	private static void acabar(BufferedReader reader, BufferedWriter writeAux) throws IOException {
		String lin = null;
		while ( (lin = reader.readLine()) != null) {
			writeAux.write(lin);
			writeAux.newLine();
		}
	}

	private static void renombrar() {
		File a = new File("auxiliar.txt");
		File m = new File("mestre.txt");
		m.delete();
		boolean correcto = a.renameTo(m);
		if (correcto)
			System.out.println("El renombrado ha sido correcto");
		else
			System.out.println("El renombrado no se ha podido realizar");

	}
}