import java.io.FileReader;
import java.io.FileWriter;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.io.Reader;
import java.io.Writer;
import java.io.IOException;
import java.util.regex.Pattern;
import java.util.regex.Matcher;
import java.util.regex.PatternSyntaxException;

public class PatternReplacer1 {

    private static final int MAX_SIZE = 1000;

    public PatternReplacer1() {}

    // Stream からの読み込み
    private String readContents(Reader reader) throws IOException {

        char[] chars = new char[10000];
        StringBuffer buffer = new StringBuffer();

        while (true) {
            int size = reader.read(chars);
            if (size < 0) {
                break;
            }
            
            buffer.append(chars, 0, size);
        }
        
        return buffer.toString();
    }

    public void replaceFirst(String regex, String replaceText,
                             Reader reader, PrintWriter writer) throws IOException {
        String contents = readContents(reader);

        replaceFirst(regex, replaceText, contents, writer);
    }

    private void replaceFirst(String regex, String replaceText,
                             String input, PrintWriter writer){
        try {
            Pattern pattern = Pattern.compile(regex);
            Matcher matcher = pattern.matcher(input);

            String result = matcher.replaceFirst(replaceText);

            writer.print(result);
        } catch (PatternSyntaxException ex) {
            System.err.println(ex.getMessage());
            ex.printStackTrace();
            return;
        }
    }

    public static void main(String[] args) {
        if (args.length < 2) {
            System.out.println("Usage: java PatternReplacer1 pattern replace [inputfile] [outputfile]");        
            return;
        }

        PatternReplacer1 replacer = new PatternReplacer1();

        try {
            Reader reader = null;
            PrintWriter writer = null;
            if (args.length == 2) {
                reader = new InputStreamReader(System.in);
                writer = new PrintWriter(new OutputStreamWriter(System.out));
            } else if (args.length == 3) {
                reader = new FileReader(args[2]);
                writer = new PrintWriter(new OutputStreamWriter(System.out));
            } else if (args.length > 3) {
                reader = new FileReader(args[2]);
                writer = new PrintWriter(new FileWriter(args[3]));
            }

            replacer.replaceFirst(args[0], args[1], reader, writer);

            reader.close();
            writer.close();
        } catch(IOException ex) {
            ex.printStackTrace();
        }
    }
}