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 PyPy3 (2.4.0) (judge verdict: Accepted)

import sys
import copy

sys.setrecursionlimit(10**6)

m = [0,2,5,5,4,5,6,3,7,6]

def a_le_b(a, b):
    la, lb = len(a), len(b)
    if la == lb:
        for i in range(la):
            if a[i] < b[i]:
                return True
            elif a[i] > b[i]:
                return False
        return True
    return la < lb

N, M = map(int, input().split())
A = list(map(int, input().split()))
A.sort(reverse=True)
for i in range(len(A)-1, 0, -1):
    for j in range(i-1, -1, -1):
        if m[A[i]] == m[A[j]]:
            del A[i]
            break
# print(A)
dp = [[] for _ in range(N+1)]

for i in range(N):
    if len(dp[i])==0 and i != 0: continue
    x = copy.copy(dp[i]) + [0]
    # print(x)
    for j in range(len(A)):
        ind = i + m[A[j]]
        if ind <= N:
            x[-1] = A[j]
            if a_le_b(dp[ind], x):
                dp[ind] = copy.copy(x)
# print(dp)
print(''.join(map(str, dp[-1])))