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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Diagnostics;
using System.Numerics;

public class Program
{
    public static void Main(string[] args)
    {
        int[] cost = new int[] { 0, 2, 5, 5, 4, 5, 6, 3, 7, 6 };
        string[] line = Console.ReadLine().Split(' ');
        int n = int.Parse(line[0]);
        int m = int.Parse(line[1]);

        int[] values = Console.ReadLine().Split(' ').Select(s => int.Parse(s)).ToArray();
        int[] costs = values.Select(i => cost[i]).ToArray();

        int min = costs.Min();
        int mDig = n / min;

        int[] dp = new int[n + 1];
        dp[0] = 0;

        for (int i = 1; i < dp.Length; i++)
        {
            dp[i] = costs.Select(x => (i >= x) ? (dp[i - x] + 1) : int.MinValue).Max();
        }

        int dig = dp[n];
        string ans = "";
        for (int i = dig - 1; i >= 0; i--)
        {
            int v = values.Where(x => (n - cost[x] >= 0) && dp[n - cost[x]] == i).Max();
            n -= cost[v];
            ans += v;
        }

        Console.WriteLine(ans);
        Console.ReadLine();
    }
}