import java.io.*; import java.util.*; public class Main_yukicoder451 { private static Scanner sc; private static Printer pr; private static void solve() { int n = sc.nextInt(); long[] b = new long[n]; for (int i = 0; i < n; i++) { b[i] = sc.nextLong(); } long[] max = new long[n + 1]; Arrays.fill(max, Long.MAX_VALUE); for (int i = 0; i < n; i++) { if (i % 2 == 0) { max[i] = Math.min(max[i], b[i] - 1); max[i + 1] = Math.min(max[i + 1], b[i] - 1); } else { long tmp = b[i - 1] - b[i]; b[i] = tmp; if (tmp < 2) { pr.println(-1); return; } max[i - 1] = Math.min(max[i - 1], tmp - 1); max[i + 1] = Math.min(max[i + 1], tmp - 1); } } for (int i = 0; i <= n; i++) { // pr.println(max[i]); if (max[i] < 1) { pr.println(-1); return; } } // long l = 0; // long r = 1_000_000_000_000_000_000L; long r = max[0]; /* while (r - l > 1) { long mid = l + (r - l) / 2; if (f(mid, b)) { r = mid; } else { l = mid; } } */ if (f(1, b)) { r = 1; } else if (f(max[0], b)) { r = max[0]; } else { // r = max[0] / 2; pr.println(-1); return; } if (f(r, b)) { long[] a = new long[n + 1]; a[0] = r; for (int i = 1; i <= n; i++) { if (i % 2 == 1) { a[i] = b[i - 1] - a[i - 1]; } else { a[i] = b[i - 1] - a[i - 2]; } } pr.println(n + 1); for (int i = 0; i <= n; i++) { pr.println(a[i]); } } else { pr.println(-1); } } private static boolean f(long mid, long[] b) { int n = b.length; long[] a = new long[n + 1]; a[0] = mid; for (int i = 1; i <= n; i++) { if (i % 2 == 1) { a[i] = b[i - 1] - a[i - 1]; } else { a[i] = b[i - 1] - a[i - 2]; } if (a[i] <= 0) { return false; } } return true; } // --------------------------------------------------- public static void main(String[] args) { sc = new Scanner(System.in); pr = new Printer(System.out); solve(); pr.close(); sc.close(); } @SuppressWarnings("unused") private static class Scanner { BufferedReader br; Scanner (InputStream in) { br = new BufferedReader(new InputStreamReader(in)); } private boolean isPrintable(int ch) { return ch >= '!' && ch <= '~'; } private boolean isCRLF(int ch) { return ch == '\n' || ch == '\r' || ch == -1; } private int nextPrintable() { try { int ch; while (!isPrintable(ch = br.read())) { if (ch == -1) { throw new NoSuchElementException(); } } return ch; } catch (IOException e) { throw new NoSuchElementException(); } } String next() { try { int ch = nextPrintable(); StringBuilder sb = new StringBuilder(); do { sb.appendCodePoint(ch); } while (isPrintable(ch = br.read())); return sb.toString(); } catch (IOException e) { throw new NoSuchElementException(); } } int nextInt() { try { // parseInt from Integer.parseInt() boolean negative = false; int res = 0; int limit = -Integer.MAX_VALUE; int radix = 10; int fc = nextPrintable(); if (fc < '0') { if (fc == '-') { negative = true; limit = Integer.MIN_VALUE; } else if (fc != '+') { throw new NumberFormatException(); } fc = br.read(); } int multmin = limit / radix; int ch = fc; do { int digit = ch - '0'; if (digit < 0 || digit >= radix) { throw new NumberFormatException(); } if (res < multmin) { throw new NumberFormatException(); } res *= radix; if (res < limit + digit) { throw new NumberFormatException(); } res -= digit; } while (isPrintable(ch = br.read())); return negative ? res : -res; } catch (IOException e) { throw new NoSuchElementException(); } } long nextLong() { try { // parseLong from Long.parseLong() boolean negative = false; long res = 0; long limit = -Long.MAX_VALUE; int radix = 10; int fc = nextPrintable(); if (fc < '0') { if (fc == '-') { negative = true; limit = Long.MIN_VALUE; } else if (fc != '+') { throw new NumberFormatException(); } fc = br.read(); } long multmin = limit / radix; int ch = fc; do { int digit = ch - '0'; if (digit < 0 || digit >= radix) { throw new NumberFormatException(); } if (res < multmin) { throw new NumberFormatException(); } res *= radix; if (res < limit + digit) { throw new NumberFormatException(); } res -= digit; } while (isPrintable(ch = br.read())); return negative ? res : -res; } catch (IOException e) { throw new NoSuchElementException(); } } float nextFloat() { return Float.parseFloat(next()); } double nextDouble() { return Double.parseDouble(next()); } String nextLine() { try { int ch; while (isCRLF(ch = br.read())) { if (ch == -1) { throw new NoSuchElementException(); } } StringBuilder sb = new StringBuilder(); do { sb.appendCodePoint(ch); } while (!isCRLF(ch = br.read())); return sb.toString(); } catch (IOException e) { throw new NoSuchElementException(); } } void close() { try { br.close(); } catch (IOException e) { // throw new NoSuchElementException(); } } } private static class Printer extends PrintWriter { Printer(PrintStream out) { super(out); } } }