import java.io.*;

public class IOStreams {
    public static boolean checkIfNumber(String line){
         if(Character.isDigit(line.charAt(0)))
             return true;
         else return false;
    }

    public static void main(String[] args) throws IOException {
        BufferedReader br=null;
        BufferedWriter bw=null;
        try {
            br = new BufferedReader(new InputStreamReader(new FileInputStream("izvor.txt")));
            bw = new BufferedWriter(new FileWriter("destinacija.txt"));

            String line = null;
            while (true) {
                line = br.readLine();
                if (line == null)
                    break;

                if (checkIfNumber(line)) {
                    bw.write(line + "\n");
                }
            }
        }finally {
            if(br!=null){
                br.close();
            }
            if(bw!=null){
                bw.flush();
                bw.close();
            }
        }
    }
}