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 matchsticks[10] = { 0, 2, 5, 5, 4, 5, 6, 3, 7, 6 };
int a[10];
int n, m, smallest, smallptr, len, sur;
bool cmp1(int a, int b)
{ return matchsticks[a] < matchsticks[b] || (matchsticks[a] == matchsticks[b] && a > b); }
bool cmp2(int a, int b) { return a > b; }
vector<int> out;
int main()
{
	ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
	cin >> n >> m;
	for (int i = 1; i <= m; i++)
		cin >> a[i];
	sort(a + 1, a + m + 1, cmp1);
	smallest = a[1];
	sort(a + 1, a + m + 1);
	for (int i = 1; i <= m; i++)
		if (a[i] == smallest)
		{
			smallptr = i;
			break;
		}
	len = n / matchsticks[smallest];
	sur = n % matchsticks[smallest];
	for (int i = 1; i < len; i++)
	{
		int num(smallest);
		for (int j = m; j > smallptr; j--)
			if (matchsticks[a[j]] - matchsticks[smallest] <= sur)
			{
				sur -= matchsticks[a[j]] - matchsticks[smallest];
				num = a[j];
				break;
			}
		out.push_back(num);
	}
	sur += matchsticks[smallest];
	for (int j = m; j; j--)
		if (matchsticks[a[j]] == sur)
		{
			out.push_back(a[j]);
			break;
		}
	sort(out.begin(), out.end(), cmp2);
	ostream_iterator<int> output(cout);
	copy(out.begin(), out.end(), output);
	cout << endl;

	return 0;
}