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)

# -*- coding: utf-8 -*-

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

cost = {1: 2, 2: 5, 3: 5, 4: 4, 5: 5, 6: 6, 7: 3, 8: 7, 9: 6}
cd = {}
for a in A:
    if cost[a] in cd:
        cd[cost[a]] = max(cd[cost[a]], a)
    else:
        cd[cost[a]] = a

dp = [(0, [])]
for i in range(1, N + 1):
    mx, mxl = int(-1e10), []
    for c in cd:
        if i - c >= 0 and mx < dp[i - c][0] + 1 and 0 <= dp[i - c][0]:
            mx, mxl = dp[i - c][0] + 1, dp[i - c][1] + [cd[c]]
    dp.append((mx, mxl))

ans = dp[-1][1]
ans.sort(reverse=True)
print(''.join(map(str, ans)))