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.Linq;

class D
{
	static void Main()
	{
		Func<int[]> read = () => Console.ReadLine().Split().Select(int.Parse).ToArray();
		var h = read();
		var n = h[0];
		var a = read().GroupBy(x => "/255456376"[x] - '0').OrderBy(g => g.Key).ToDictionary(g => g.Key, g => g.Max());

		var dp = new int[50][];
		for (int i = 0; i < dp.Length; i++)
		{
			var c = a.Keys.FirstOrDefault(x => i >= x && dp[i - x] != null);
			dp[i] = c != 0 ? dp[i - c].Concat(new[] { c }).ToArray() : a.Keys.Any(x => x == i) ? new[] { i } : null;
		}

		if (n < dp.Length)
		{
			Console.WriteLine(string.Join("", dp[n].Select(c => a[c]).OrderByDescending(x => x)));
		}
		else
		{
			var c0 = a.Keys.First();
			var k = (n - dp.Length + c0) / c0;
			var t = string.Join("", dp[n - k * c0].Select(c => a[c]).OrderByDescending(x => x));
			var cd = a[c0].ToString()[0];
			Console.WriteLine(t.Insert(t.IndexOf(cd), new string(cd, k)));
		}
	}
}