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>
#define err(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)

using namespace std;

typedef long long ll;

vector<int> cnt = { 0, 2, 5, 5, 4, 5, 6, 3, 7, 6 };

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);
	int n, m;
	cin >> n >> m;
	
	
	vector<int> A(m);
	for (int i = 0; i < m; i++) cin >> A[i];
	
	vector<int> dp(n + 1, -1), p(n + 1, -1);
	
	dp[0] = 0;
	for (int i = 0; i < n; i++) if (dp[i] != -1) {
		for (int c : A) if (i + cnt[c] <= n && dp[i + cnt[c]] < dp[i] + 1)
			dp[i + cnt[c]] = dp[i] + 1, p[i + cnt[c]] = c;
	}
	
	string ans;
	for (int i = n; i; i -= cnt[p[i]]) ans += (char)('0' + p[i]);
	sort(ans.rbegin(), ans.rend());
	cout << ans << "\n";
	return 0;
}