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 Python (3.4.3) (judge verdict: Runtime Error)

N, M = map(int, input().split())
A = list(map(int, input().split()))

def dfs(choices, s, cost, i):
    if i == len(choices):
        return -1
    if cost == 0:
        return int(s)
    if cost < 0:
        return -1
    
    if choices[i][0] == 1:
        if cost % 2 == 0:
            return int(s + (cost // 2) * '1')
        else:
            return -1
    
    
    tmp1 = dfs(
        choices,
        s + str(choices[i][0]),
        cost - choices[i][1],
        i
    )
    if i+1 == len(choices):
        tmp2 = -1
    else:
        tmp2 = dfs(
            choices,
            s,
            cost,
            i + 1
        )
    
    ret = max(tmp1, tmp2)
    return ret

match = [-100,2,5,5,4,5,6,3,7,6]
choices = []
for i in A:
    if (i == 6) and (9 in A):
        continue
    if (i == 3) and (5 in A):
        continue
    if (i == 2) and (3 in A or 5 in A):
        continue
    choices.append([i, match[i]])

choices.sort(reverse=True)

ans = dfs(choices, '', N, 0)
print(ans)