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.Generic;
using System.Linq;


namespace CSTest
{
    class Program
    {
        private static int[] needsMatch = {0, 2, 5, 5, 4, 5, 6, 3, 7, 6};

        static void Main(string[] args)
        {
            var strings = Console.ReadLine().Split(new[] {' '});
            int N = int.Parse(strings[0]);
            int M = int.Parse(strings[1]);
            strings = Console.ReadLine().Split(new[] {' '});
            var list = strings.Select(int.Parse).OrderBy(val => needsMatch[val]).ThenByDescending(val => val).ToList();
            var result = Search(N, list, new List<int>());
            result.Sort((val1, val2) => val2 - val1);
            result.ForEach(Console.Write);
            Console.WriteLine();
        }

        static List<int> Search(int N, List<int> canUseList, List<int> list)
        {
            if (N == 0) return list;
            if (N < 0) return null;
            foreach (var i in canUseList)
            {
                var newList = new List<int>();
                newList.AddRange(list);
                newList.Add(i);
                var r = Search(N - needsMatch[i], canUseList, newList);
                if (r != null) return r;
            }

            return null;
        }
    }
}