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: Wrong Answer)

def solve(pos, rest, a):
    if pos == len(a):
        if rest == 0:
            return True
        else:
            return False

    digit, match = a[pos]
    for k in range(rest // match, -1, -1):
        if solve(pos + 1, rest - match * k, a):
            ans[pos] = k
            return True
    return False

m = [0, 2, 5, 5, 4, 5, 6, 3, 7, 6]
N, M = map(int, input().split())
c = list(map(int, input().split()))
a = [(i, m[i]) for i in c]
a.sort(key=lambda x:x[1])
pd, pm = a[0]
b = []
for d, m in a[1:]:
    if pm == m:
        if pd < d:
            pd = d
    else:
        b.append((pd, pm))
        pm = m
        pd = d
b.append((pd, pm))
ans = [0] * len(b)
solve(0, N, b)
ans2 = []
for i in range(len(ans)):
    ans2.append((b[i][0], ans[i]))
ans2.sort(reverse=True)
for d, c in ans2:
    print(str(d)*c, end="")
print()