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<Problem> {

		@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<Problem> {

		@Override
		public String solve(Problem problem) {
			// TODO
			return null;
		}
	}
	
	class Factory implements IProblemFactory<Problem> {

		@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<Problem> processor;
	
	Main() {
		Init();
	}
	
	void Init() {
		ProblemProcessorConfig<Problem> config = new ProblemProcessorConfig<>();
		
		config.factory = new Factory();
		config.solver = new Solver();
		config.solver2 = new Solver2();
		
		processor = new ProblemProcessor<Problem>(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<P extends IProblem> {
		
		abstract P newProblem();
		abstract P newProblem(ProblemReader reader) throws IOException;
	}
	
	interface IProblemSolver<P extends IProblem> {
		
		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<P extends IProblem> {
		
		IProblemFactory<P> factory;
		
		ProblemCreator(IProblemFactory<P> factory) {
			this.factory = factory;
		}
		
		void create() throws FileNotFoundException {
			P problem = factory.newProblem();
			System.out.println(problem.toString());
		}
	}
	
	class ProblemSolverComparator<P extends IProblem> {
		
		IProblemFactory<P> factory;
		IProblemSolver<P> solver1, solver2;
		
		ProblemSolverComparator(IProblemFactory<P> factory, IProblemSolver<P> solver1, IProblemSolver<P> 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<P extends IProblem> {
		
		IProblemFactory<P> factory;
		IProblemSolver<P> solver;
		
		ProblemAnswerer(IProblemFactory<P> factory, IProblemSolver<P> 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<P extends IProblem> {
		
		IProblemFactory<P> factory;
		
		IProblemSolver<P> solver, solver2;
	}
	
	class ProblemProcessor<P extends IProblem> {
		
		ProblemProcessorConfig<P> config;
		
		ProblemCreator<P> creator;
		ProblemSolverComparator<P> comparator;
		ProblemAnswerer<P> answerer;
		
		ProblemProcessor(ProblemProcessorConfig<P> config) {
			this.config = config;
			creator = new ProblemCreator<P>(config.factory);
			comparator = new ProblemSolverComparator<P>(config.factory, config.solver, config.solver2);
			answerer = new ProblemAnswerer<P>(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(" ");
		}
	}
}