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 Kotlin (1.0.0) (judge verdict: Time Limit Exceeded)

import java.util.*

val x = intArrayOf(0, 2, 5, 5, 4, 5, 6, 3, 7, 6)
val nums = mutableSetOf<String>()

fun main(args: Array<String>) {

    val n = readLine()!!.split(" ").map { it.toInt() }
    val a = readLine()!!.split(" ").map { it.toInt() }
        .sortedDescending()
        .distinctBy { it -> x[it] }
        .sortedDescending()

    for (i in a.indices) {
        find("", n[0], a.drop(i))
    }
    
    println(nums.maxWith(Comparator { o1, o2 ->
        val len1 = o1.length
        val len2 = o2.length

        if (len1 != len2) {
            return@Comparator len1 - len2
        }

        for (i in 0 until len1) {
            val v1 = o1[i]
            val v2 = o2[i]
            if (v1 != v2) {
                return@Comparator v1 - v2
            }
        }

        0
    }))

}

fun find(ans: String, rest: Int, a: List<Int>): String {
    if (rest == 0) {
        return ans
    } else if (rest < 0) {
        return "-1"
    }

    loop@ for ((i, v) in a.withIndex()) {
        val k = rest - x[v]
        val str = find(ans + v.toString(), k, a.drop(i))
        if (str != "-1") {
            nums.add(str)
        }
    }
    return "-1"
}