import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.*;
 
class Ideone {
  public static void solve(String s) throws java.lang.Exception {
    Pattern p = Pattern.compile("(\\b\\w+\\b)(?=[\\s\\S]*\\b\\1\\b[\\s\\S]*\\b\\1\\b)", Pattern.UNICODE_CHARACTER_CLASS);
    String res = p.matcher(s+" "+s).replaceAll("_$1");
    res = res.substring(0, res.length() - 1 - p.matcher(s).replaceAll("_$1").length());
 
    System.out.println(s);
    System.out.println();
    System.out.println(res);
    System.out.println();
  }
 
  public static void main(String[] args) throws java.lang.Exception {
    solve("This is a test\nAnd this is also a test\nAnd these are also tests\ntest\nЭто тест\nЭто также тест\nИ это также тесты");
    solve("Du hast mich gefragt\nDu hast mich gefragt und ich hab nichts gesagt");
  }
}

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