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: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;

int main(int argc, char const *argv[])
{
	int n,m,use[9]={2,5,5,4,5,6,3,7,6};
	cin>>n>>m;
	int a[m],mi=10,b=-1,memo[10]={};
	for (int i = 0; i < m; ++i)
	{
		cin>>a[i];--a[i];
		memo[a[i]+1]=1;
		if (mi>=use[a[i]])
		{
			mi=use[a[i]];
			b=max(b,a[i]+1);
		}
	}
	sort(a,a+m);
	reverse(a,a+m);
	int dp[n+20];
	for (int i = 0; i < n+20; ++i)
	{
		dp[i]=-1000000;
	}
	dp[0]=0;
	for (int i = 0; i < n; ++i)
	{
		for (int j = 0; j < m; ++j)
		{
			dp[i+use[a[j]]]=max(dp[i+use[a[j]]],dp[i]+1);
		}
	}
	string ans="";
	while (n>0)
	{
		for (int i = 0; i < m; ++i)
		{
			if (dp[n]-1==dp[n-use[a[i]]])
			{
				ans+='1'+a[i];
				n-=use[a[i]];
				break;
			}
		}
	}
	sort(ans.begin(), ans.end());
	reverse(ans.begin(), ans.end());
	cout<<ans<<endl;
	return 0;
}