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: Runtime Error)

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

namespace ABC118D
{
    public partial class Program
    {
        void Solve(StreamScanner ss, StreamWriter sw)
        {
            var N = ss.Next(int.Parse);
            var M = ss.Next(int.Parse);
            var A = ss.Next(int.Parse, M);

            var match = new[] {99, 2, 5, 5, 4, 5, 6, 3, 7, 6}.ToArray();
            var min = match.Where((_, i) => A.Contains(i)).Min();
            var s = A.Where(x => match[x] == min).Max();
            var sc = N / match[s];

            var t = -1;
            while (true)
            {
                var cnt = N - sc * match[s];
                t = DFS(new List<int>(), A, match, cnt, 0);
                if (t >= 0) break;
                sc--;
            }

            var ret = new string((char)(s + '0'), sc) + t.ToString();
            sw.WriteLine(string.Join("", ret.OrderByDescending(x => x)));
            //---------------------------------
        }

        int DFS(List<int> list, int[] A, int[] match, int cnt, int cur)
        {
            if (cur > cnt)
            {
                return -1;
            }

            if (cur == cnt)
            {
                return int.Parse(string.Join("", list.OrderByDescending(x => x)));
            }

            var ret = -1;

            foreach (var a in A)
            {
                list.Add(a);
                ret = Math.Max(ret, DFS(list, A, match, cnt, cur + match[a]));
                list.Remove(a);
            }

            return ret;
        }
    }

    public class StreamScanner
    {
        static readonly char[] Separator = { ' ' };
        readonly StreamReader streamReader;

        string[] line = new string[0];
        int index = 0;

        public bool EndOfStream { get { return streamReader.EndOfStream && index >= line.Length; } }

        public StreamScanner(Stream stream)
        {
            this.streamReader = new StreamReader(stream);
        }

        public string Next()
        {
            return Next(s => s);
        }

        public string[] Next(int x)
        {
            return Next(s => s, x);
        }

        public string[][] Next(int x, int y)
        {
            return Next(s => s, x, y);
        }

        public T Next<T>(Func<string, T> parser)
        {
            if (EndOfStream) throw new EndOfStreamException();
            if (index < line.Length) return parser(line[index++]);
            index = 0;
            line = streamReader.ReadLine()?.Split(Separator, StringSplitOptions.RemoveEmptyEntries);
            return Next(parser);
        }

        public T[] Next<T>(Func<string, T> parser, int x)
        {
            var ret = new T[x];
            for (var i = 0; i < x; ++i) ret[i] = Next(parser);
            return ret;
        }

        public T[][] Next<T>(Func<string, T> parser, int x, int y)
        {
            var ret = new T[y][];
            for (var i = 0; i < y; ++i) ret[i] = Next(parser, x);
            return ret;
        }
    }

    public partial class Program
    {
        static void Main()
        {
            Excute(Console.OpenStandardInput(), Console.OpenStandardOutput());
        }

        public static void Excute(Stream input, Stream output)
        {
            var ss = new StreamScanner(input);
            var sw = new StreamWriter(output);
            new Program().Solve(ss, sw);
            sw.Flush();
        }
    }
}