define the SequencedLine class

src/main/java/model/SequencedLine.java

+package model;
+
+public class SequencedLine implements Comparable<SequencedLine> {
+    private final int sequenceNumber;
+    private final String line;
+
+    public SequencedLine(int sequenceNumber, String line) {
+        this.sequenceNumber = sequenceNumber;
+        this.line = line;
+    }
+
+    public int getSequenceNumber() {
+        return sequenceNumber;
+    }
+
+    public String getLine() {
+        return line;
+    }
+
+    /**
+     * Defines the natural ordering of SequencedLine objects
+     * Lines with lower sequence numbers have higher priority
+     */
+    @Override
+    public int compareTo(SequencedLine other) {
+        return Integer.compare(this.sequenceNumber, other.sequenceNumber);
+    }
+
+    @Override
+    public String toString() {
+        return "SequencedLine{sequence=" + sequenceNumber + ", line='" + line + "'}";
+    }
+}
\ No newline at end of file