import java.util.Arrays; public class Main { private static void solve() { int n = ni(); int[] a = na(n); long[] list = new long[500000]; int ptr = 0; while (true) { long x = 0; for (int v : a) { x *= v >= 10 ? 100 : 10; x += v; } list[ptr++] = x; if (!nextPermutation(a)) { break; } } list = Arrays.copyOf(list, ptr); Arrays.sort(list); for (int i = ptr - 1; i >= 0; i--) { if (doMirrorRabin(list[i])) { System.out.println(list[i]); return; } } System.out.println(-1); } public static boolean doMirrorRabin(long n) { int[] P = {2, 3, 5, 7, 11, 13, 17, 19, 23}; // n=long int s = Long.numberOfTrailingZeros(n - 1); long d = n - 1 >> s; outer: for (int a : P) { if (a >= n) continue; long mul = a; long ad = 1; for (long e = d; e > 0; e >>>= 1) { if ((e & 1) == 1) ad = mul(ad, mul, n); mul = mul(mul, mul, n); } if (ad == 1) continue; for (int r = 0; r < s; r++) { if (ad == n - 1) continue outer; ad = mul(ad, ad, n); } return false; } return true; } public static long mul(long a, long b, long mod) { if (a >= mod || a < 0) a %= mod; if (a < 0) a += mod; if (b >= mod || b < 0) b %= mod; if (b < 0) b += mod; long ret = 0; int x = 63 - Long.numberOfLeadingZeros(b); for (; x >= 0; x--) { ret += ret; if (ret >= mod) ret -= mod; if (b << ~x < 0) { ret += a; if (ret >= mod) ret -= mod; } } return ret; } public static boolean nextPermutation(int[] a) { int n = a.length; int i; for (i = n - 2; i >= 0 && a[i] >= a[i + 1]; i--); if (i == -1) return false; int j; for (j = i + 1; j < n && a[i] < a[j]; j++); int d = a[i]; a[i] = a[j - 1]; a[j - 1] = d; for (int p = i + 1, q = n - 1; p < q; p++, q--) { d = a[p]; a[p] = a[q]; a[q] = d; } return true; } public static void main(String[] args) { new Thread(null, new Runnable() { @Override public void run() { long start = System.currentTimeMillis(); String debug = args.length > 0 ? args[0] : null; if (debug != null) { try { is = java.nio.file.Files.newInputStream(java.nio.file.Paths.get(debug)); } catch (Exception e) { throw new RuntimeException(e); } } reader = new java.io.BufferedReader(new java.io.InputStreamReader(is), 32768); solve(); out.flush(); tr((System.currentTimeMillis() - start) + "ms"); } }, "", 64000000).start(); } private static java.io.InputStream is = System.in; private static java.io.PrintWriter out = new java.io.PrintWriter(System.out); private static java.util.StringTokenizer tokenizer = null; private static java.io.BufferedReader reader; public static String next() { while (tokenizer == null || !tokenizer.hasMoreTokens()) { try { tokenizer = new java.util.StringTokenizer(reader.readLine()); } catch (Exception e) { throw new RuntimeException(e); } } return tokenizer.nextToken(); } private static double nd() { return Double.parseDouble(next()); } private static long nl() { return Long.parseLong(next()); } private static int[] na(int n) { int[] a = new int[n]; for (int i = 0; i < n; i++) a[i] = ni(); return a; } private static char[] ns() { return next().toCharArray(); } private static long[] nal(int n) { long[] a = new long[n]; for (int i = 0; i < n; i++) a[i] = nl(); return a; } private static int[][] ntable(int n, int m) { int[][] table = new int[n][m]; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { table[i][j] = ni(); } } return table; } private static int[][] nlist(int n, int m) { int[][] table = new int[m][n]; for (int i = 0; i < n; i++) { for (int j = 0; j < m; j++) { table[j][i] = ni(); } } return table; } private static int ni() { return Integer.parseInt(next()); } private static void tr(Object... o) { if (is != System.in) System.out.println(java.util.Arrays.deepToString(o)); } }