// date:17.4.3

// author: linyang <linyang@xiaomi.com>

import java.io.*;

import java.util.*;

import static java.lang.System.out;

public class ReplaceText {

public static void main(String[] args) throws Exception {

if (args.length != 4) {

out.println("usage: java ReplaceText sourceFile targetFile oldStr newStr");

System.exit(0);

}

File sourceFile = new File(args[0]);

if (!sourceFile.exists()) {

out.println("sourceFile " + args[0] + " does not exists");

System.exit(0);

}

File targetFile = new File(args[1]);

if (targetFile.exists()) {

out.println("targetFile " + args[1] + " already exists");

System.exit(0);

}

Scanner input = new Scanner(sourceFile);

PrintWriter output = new PrintWriter(targetFile);

while (input.hasNext()) {

String s1 = input.nextLine();

String s2 = s1.replaceAll(args[2], args[3]);

output.println(s2);

}

input.close();

output.close();

}

}