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: Runtime Error)

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int m = in.nextInt();
		List<int[]> list = new ArrayList<>();
		for(int i=0;i<m;i++) {
			int[] tmp = new int[2];
			tmp[0] = in.nextInt();
			if(tmp[0]==1) tmp[1] = 2;
			else if(tmp[0]==7) tmp[1] = 3;
			else if(tmp[0]==4) tmp[1] = 4;
			else if(tmp[0]==2 || tmp[0]==3 || tmp[0]==5) tmp[1] = 5;
			else if(tmp[0]==6 || tmp[0]==9) tmp[1] = 6;
			else tmp[1] = 7;
			list.add(tmp);
		}
		int[] dp = new int[n+1];
		for(int i=2;i<=n;i++) {
			for(int j=0;j<list.size();j++) {
				int match = list.get(j)[1];
				if(i-match>=0) {
					dp[i] = Math.max(dp[i], dp[i-match]+1);
				}
			}
		}
		list.sort((a,b)->(-a[0]+b[0]));
		String ans = "";
		int ptr = 0;
		int i = n;
		int digit = dp[n];
		while(true) {
			if(digit==1) {
				if(i-list.get(ptr)[1]==0) {
					ans += list.get(ptr)[0];
					break;
				}else ptr++;
			}else if(i-list.get(ptr)[1]>=0){
				if(dp[i-list.get(ptr)[1]]>=digit-1) {
					ans += list.get(ptr)[0];
					i -= list.get(ptr)[1];
					digit--;
				}
			}else ptr++;
		}
		System.out.println(ans);
		in.close();
	}

}