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++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <iostream>
#include <stdio.h>
#include <string>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <math.h>
#include <vector>
#include <algorithm>
#include <queue>
#include <stack>
#include <climits>
#include <bitset>
#include <list>
#include <map>
#include <set>

using namespace std;

typedef unsigned long long ull;
typedef long long ll;

int num[]={0, 2, 5, 5, 4, 5, 6, 3, 7, 6};
string s[10010];

int main(){
	int n, m;
	cin >> n >> m;
	int a[m];
	for(int i=0; i<m; i++) cin >> a[i];
	for(int i=0; i<=1010; i++) s[i]="0";
	s[0]="";
	
	for(int i=1; i<=n; i++){
		for(int j=0; j<m; j++){
			int k=i-num[a[j]];
			if(k<0) continue;
			if(s[k]=="0") continue;
 
			string t=s[k]+to_string(a[j]);
			if(s[i]=="") s[i]=t;
			else if(s[i].length()==t.length()){
				s[i]=max(s[i], t);
			}else if(s[i].length()<t.length()){
				s[i]=t;
			}
		}
	}
	cout << s[n] << endl;
	return 0;
}