import java.io.BufferedReader; import java.io.FileNotFoundException; import java.io.IOException; import java.io.InputStreamReader; public class Main { /** * This class represents a problem setting. */ class Problem implements IProblem { int D; int[] a; @Override public void set(ProblemReader reader) throws IOException { D = reader.nextInt(); a = reader.nextIntArray(); } @Override public String toString() { // TODO return null; } } /** * Solver for the problem. * It's the most important part of codes in this file. */ class Solver implements IProblemSolver { @Override public String solve(Problem problem) { int D = problem.D; int[] a = problem.a; int[] res = solve(D, a); if (res.length == 1 && res[0] == 0) { return "0\n0"; } else { return (res.length - 1) + "\n" + StringUtils.toString(res); } } private int[] solve(int D, int[] a) { for (int i = D; i >= 3; i--) { a[i - 2] += a[i]; a[i] = 0; } if (D >= 2 && a[2] != 0) { return new int[]{a[0], a[1], a[2]}; } else if (D >= 1 && a[1] != 0) { return new int[]{a[0], a[1]}; } else { return new int[]{a[0]}; } } } /** * This class is a solver to confirm the main solver. * This solver often works only for a problem with a small number setting. */ class Solver2 implements IProblemSolver { @Override public String solve(Problem problem) { // TODO return null; } } class Factory implements IProblemFactory { @Override public Problem newProblem() { // TODO return null; } @Override public Problem newProblem(ProblemReader reader) throws IOException { Problem problem = new Problem(); problem.set(reader); return problem; } } ProblemProcessor processor; Main() { Init(); } void Init() { ProblemProcessorConfig config = new ProblemProcessorConfig<>(); config.factory = new Factory(); config.solver = new Solver(); config.solver2 = new Solver2(); processor = new ProblemProcessor(config); } void process(String mode) throws IOException { processor.process(mode); } public static void main(String args[]) throws IOException { String mode = "solve"; new Main().process(mode); } /* Common library */ interface IProblem { abstract void set(ProblemReader reader) throws IOException; } interface IProblemFactory

{ abstract P newProblem(); abstract P newProblem(ProblemReader reader) throws IOException; } interface IProblemSolver

{ abstract String solve(P problem); } class ProblemReader { BufferedReader br = null; ProblemReader() { br = new BufferedReader(new InputStreamReader(System.in)); } int nextInt() throws IOException { return StringUtils.toInt(br.readLine()); } long nextLong() throws IOException { return StringUtils.toLong(br.readLine()); } double nextDouble() throws IOException { return StringUtils.toDouble(br.readLine()); } String nextString() throws IOException { return br.readLine(); } int[] nextIntArray() throws IOException { return StringUtils.toIntArray(br.readLine()); } long[] nextLongArray() throws IOException { return StringUtils.toLongArray(br.readLine()); } double[] nextDoubleArray() throws IOException { return StringUtils.toDoubleArray(br.readLine()); } String[] nextStringArray() throws IOException { return StringUtils.toStringArray(br.readLine()); } int[] nextIntArray(int n) throws IOException { int[] a = new int[n]; for (int i = 0; i < n; i++) { a[i] = nextInt(); } return a; } long[] nextLongArray(int n) throws IOException { long[] a = new long[n]; for (int i = 0; i < n; i++) { a[i] = nextLong(); } return a; } double[] nextDoubleArray(int n) throws IOException { double[] a = new double[n]; for (int i = 0; i < n; i++) { a[i] = nextDouble(); } return a; } String[] nextStringArray(int n) throws IOException { String[] strs = new String[n]; for (int i = 0; i < n; i++) { strs[i] = nextString(); } return strs; } int[][] nextIntArray2(int n) throws IOException { int[][] a = new int[n][]; for (int i = 0; i < n; i++) { a[i] = nextIntArray(); } return a; } long[][] nextLongArray2(int n) throws IOException { long[][] a = new long[n][]; for (int i = 0; i < n; i++) { a[i] = nextLongArray(); } return a; } double[][] nextDoubleArray2(int n) throws IOException { double[][] a = new double[n][]; for (int i = 0; i < n; i++) { a[i] = nextDoubleArray(); } return a; } String[][] nextStringArray2(int n) throws IOException { String[][] strs = new String[n][]; for (int i = 0; i < n; i++) { strs[i] = nextStringArray(); } return strs; } void close() throws IOException { if (br != null) { br.close(); } } } class ProblemCreator

{ IProblemFactory

factory; ProblemCreator(IProblemFactory

factory) { this.factory = factory; } void create() throws FileNotFoundException { P problem = factory.newProblem(); System.out.println(problem.toString()); } } class ProblemSolverComparator

{ IProblemFactory

factory; IProblemSolver

solver1, solver2; ProblemSolverComparator(IProblemFactory

factory, IProblemSolver

solver1, IProblemSolver

solver2) { this.factory = factory; this.solver1 = solver1; this.solver2 = solver2; } void compare() throws IOException { ProblemReader reader = null; try { reader = new ProblemReader(); P problem = factory.newProblem(reader); String res1 = solver1.solve(problem); String res2 = solver2.solve(problem); if (res1.equals(res2)) { System.out.println(res1); } else { System.err.println(res1 + " " + res2); } } finally { if (reader != null) { reader.close(); } } } } class ProblemAnswerer

{ IProblemFactory

factory; IProblemSolver

solver; ProblemAnswerer(IProblemFactory

factory, IProblemSolver

solver) { this.factory = factory; this.solver = solver; } void answer() throws IOException { ProblemReader reader = null; try { reader = new ProblemReader(); P problem = factory.newProblem(reader); String res = solver.solve(problem); System.out.println(res); } finally { if (reader != null) { reader.close(); } } } } class ProblemProcessorConfig

{ IProblemFactory

factory; IProblemSolver

solver, solver2; } class ProblemProcessor

{ ProblemProcessorConfig

config; ProblemCreator

creator; ProblemSolverComparator

comparator; ProblemAnswerer

answerer; ProblemProcessor(ProblemProcessorConfig

config) { this.config = config; creator = new ProblemCreator

(config.factory); comparator = new ProblemSolverComparator

(config.factory, config.solver, config.solver2); answerer = new ProblemAnswerer

(config.factory, config.solver); } void process(String mode) throws IOException { switch (mode) { case "create": creator.create(); break; case "debug": comparator.compare(); break; case "solve": answerer.answer(); break; } } } static class StringUtils { static String toString(int a) { return String.valueOf(a); } static String toString(long a) { return String.valueOf(a); } static String toString(double a) { return String.valueOf(a); } static String toString(String str) { return str; } static String toString(int[] a) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < a.length; i++) { if (i < a.length - 1) { sb.append(a[i] + " "); } else { sb.append(a[i]); } } return sb.toString(); } static String toString(long[] a) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < a.length; i++) { if (i < a.length - 1) { sb.append(a[i] + " "); } else { sb.append(a[i]); } } return sb.toString(); } static String toString(double[] a) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < a.length; i++) { if (i < a.length - 1) { sb.append(a[i] + " "); } else { sb.append(a[i]); } } return sb.toString(); } static String toString(String[] strs) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < strs.length; i++) { if (i < strs.length - 1) { sb.append(strs[i] + " "); } else { sb.append(strs[i]); } } return sb.toString(); } static String toString(int[][] a) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < a.length; i++) { for (int j = 0; j < a[i].length; j++) { if (j < a[i].length - 1) { sb.append(a[i][j] + " "); } else { sb.append(a[i][j]); } } sb.append("\n"); } sb.setLength(sb.length() - 1); return sb.toString(); } static String toString(long[][] a) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < a.length; i++) { for (int j = 0; j < a[i].length; j++) { if (j < a[i].length - 1) { sb.append(a[i][j] + " "); } else { sb.append(a[i][j]); } } sb.append("\n"); } sb.setLength(sb.length() - 1); return sb.toString(); } static String toString(double[][] a) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < a.length; i++) { for (int j = 0; j < a[i].length; j++) { if (j < a[i].length - 1) { sb.append(a[i][j] + " "); } else { sb.append(a[i][j]); } } sb.append("\n"); } sb.setLength(sb.length() - 1); return sb.toString(); } static String toString(String[][] a) { StringBuilder sb = new StringBuilder(); for (int i = 0; i < a.length; i++) { for (int j = 0; j < a[i].length; j++) { if (j < a[i].length - 1) { sb.append(a[i][j] + " "); } else { sb.append(a[i][j]); } } sb.append("\n"); } sb.setLength(sb.length() - 1); return sb.toString(); } static int toInt(String s) throws IOException { return Integer.parseInt(s); } static long toLong(String s) throws IOException { return Long.parseLong(s); } static double toDouble(String s) throws IOException { return Double.parseDouble(s); } static int[] toIntArray(String s) throws IOException { String[] tokens = s.split(" "); int[] a = new int[tokens.length]; for (int i = 0; i < tokens.length; i++) { a[i] = Integer.parseInt(tokens[i]); } return a; } static long[] toLongArray(String s) throws IOException { String[] tokens = s.split(" "); long[] a = new long[tokens.length]; for (int i = 0; i < tokens.length; i++) { a[i] = Long.parseLong(tokens[i]); } return a; } static double[] toDoubleArray(String s) throws IOException { String[] tokens = s.split(" "); double[] a = new double[tokens.length]; for (int i = 0; i < tokens.length; i++) { a[i] = Double.parseDouble(tokens[i]); } return a; } static String[] toStringArray(String s) throws IOException { return s.split(" "); } } }