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: Wrong Answer)

fun main(args : Array<String>) {
    val (N, M) = readLine()!!.split(" ").map { it.toInt() }
    val A = readLine()!!.split(" ").map { it.toCharArray()[0] }
    val numToCost = mapOf(
            '1' to 2,
            '2' to 5,
            '3' to 5,//
            '4' to 4, //4
            '5' to 5,
            '6' to 6,
            '7' to 3,//
            '8' to 7,//
            '9' to 6
    )
    val dp = Array(N + 1, { "" })
    fun isNewBiggerThanOld(new: String, old: String) : Boolean {
        if (new.length != old.length) {
            return new.length > old.length
        }

        var i = 0
        while (i < new.length) {
            if (new[i] > old[i]) {
                return true
            }
            i++
        }
        // Other
        return false
    }

    fun generateNext(str: String, number: Char) : String {
        val buffer = StringBuffer()
        var used = false
        str.forEach {
            if (!used && number > it) {
                buffer.append(number)
                buffer.append(it)
                used = true
            } else {
                buffer.append(it)
            }
        }

        if (!used) {
            buffer.append(number)
            used = true
        }

        return buffer.toString()
    }

    (1..N).forEach { i ->
        var max = dp[i]
        A.forEach {
            val num = it
            val cost = numToCost[num]!!
            // try others
            if (i - cost >= 0) {
                if (dp[i-cost] == "") {
                    if (i - cost == 0) {
                        max = num.toString()
                    }
                } else {
                    val new = generateNext(dp[i-cost], num)
                    if (isNewBiggerThanOld(new, max)) {
                        max = new
                    }
                }
            }
        }
        dp[i] = max
    }
    println(dp[N])
}