add method to convert semester to board size

src/GameController.java

@@ -12,6 +12,10 @@ public class GameController {
 
 	// Connection timeout for client sockets in milliseconds
 	public static final int CONNECTION_TIMEOUT = 10 * 1000;
+
+	public static int semesterToBoardSize(int semester) {
+		return semester + 13;
+	}
 	
 	public HashMap<String, Class<? extends OnlinePlayer>> supportedVersions = new HashMap<>(Map.of(
 		"1.1.0", OnlinePlayer_1_1_0.class