Problem:
Score : 400 points

Problem Statement

Find the largest integer that can be formed with exactly N matchsticks, under the following conditions:

Every digit in the integer must be one of the digits A_1, A_2, ..., A_M (1 \leq A_i \leq 9).

The number of matchsticks used to form digits 1, 2, 3, 4, 5, 6, 7, 8, 9 should be 2, 5, 5, 4, 5, 6, 3, 7, 6, respectively.

Constraints

All values in input are integers.

2 \leq N \leq 10^4

1 \leq M \leq 9

1 \leq A_i \leq 9

A_i are all different.

There exists an integer that can be formed by exactly N matchsticks under the conditions.

Input

Input is given from Standard Input in the following format:

N M
A_1 A_2 ... A_M

Output

Print the largest integer that can be formed with exactly N matchsticks under the conditions in the problem statement.

Sample Input 1

20 4
3 7 8 4

Sample Output 1

777773

The integer 777773 can be formed with 3 + 3 + 3 + 3 + 3 + 5 = 20 matchsticks, and this is the largest integer that can be formed by 20 matchsticks under the conditions.

Sample Input 2

101 9
9 8 7 6 5 4 3 2 1

Sample Output 2

71111111111111111111111111111111111111111111111111

The output may not fit into a 64-bit integer type.

Sample Input 3

15 3
5 4 6

Sample Output 3

654

Solution in C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

namespace AtCoder
{
	class MainClass
	{
		private static List<int> DigitsMats = new List<int>{ -1, 2, 5, 5, 4, 5, 6, 3, 7, 6 };

		public static void Main (string[] args)
		{
			var line = Console.ReadLine ().Split (' ');
			var n = int.Parse (line [0]);
			var m = int.Parse (line [1]);

			var digits = Console.ReadLine ().Split (' ').Select (s => int.Parse (s)).ToList ();

			var matches = Divisor (n);

			MergeUnusable (matches,digits);
			var res = ToString (matches);

			Console.WriteLine ("{0}", res);
		}

		// 昇順で入っているはず
		public static List<int> Divisor (int a)
		{
			var res = new List<int> ();

			while (a != 1) {

				// まあ大丈夫だろ
				for (int b = 2; b <= 7; ++b) {
					if (a % b == 0) {
						res.Add (b);
						a = a / b;
						break;
					}
				}

			}

			return res;
		}

		public static void MergeUnusable (List<int> list,List<int> digits)
		{
			bool x2 = !digits.Contains (2);
			bool x3 = !digits.Contains (3);
			bool x4 = !digits.Contains (4);
			bool x6 = !digits.Contains (6);

			if (x2) {
				while (true) {
					int i = list.IndexOf (2);
					if (i <= 0)
						break;

					if (x6) {
						list.RemoveAt (i);
						list.RemoveAt (i);
						list.Add (4);
					} else {
						//6
						list.RemoveAt (i);
						list.Remove (3);
						list.Add (6);
					}
				}
			}

			if (x3) {
				while (true) {
					int i = list.IndexOf (3);
					if (i <= 0)
						break;

					list.RemoveAt (i);
					list.Remove (2);
					list.Add (6);
				}
			}
		}

		public static string ToString (List<int> list)
		{
			return list
				.Select (c => DigitsMats.LastIndexOf (c).ToString ())
				.OrderByDescending ((id) => id)
				.Aggregate ("", (a, b) => a + b);
		}
	}
}