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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;
import java.util.ArrayList;
public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int m = sc.nextInt();
		ArrayList<Integer> list=new ArrayList<>();
		int[] set={0,2,5,5,4,5,6,3,7,6};
		int[] a=new int[m];
		String[] dp=new String[n+1];
		dp[0]="";
		for(int i = 0; i<m; i++){
			a[i]= sc.nextInt();
		}
		for(int i = 0; i<=n; i++){
			for(int j = 0; j<m; j++){
				if(i>=set[a[j]] && dp[i-set[a[j]]]!=null){
					if(check(dp[i-set[a[j]]]+a[j],dp[i])){
						dp[i]=dp[i-set[a[j]]]+a[j];
					}
				}
			}
		}
		System.out.println(dp[n]);
	}
	static boolean check(String a,String b){
		if(b==null || a.length()>b.length()){
			return true;
		}
		if(a.length()<b.length()){
			return false;
		}
		return a.compareTo(b)>0;
	}
}