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: Time Limit Exceeded)

def main():
	n, m = list(map(int, input().split()))
	nums = list(map(int, input().split()))
	
	d = {1:2, 2:5, 3:5, 4:4, 5:5, 6:6, 7:3, 8:7, 9:6}
	num2match = {key:val for key, val in d.items() if key in nums}
	
	dp = [-1 for i in range(n + 1)]

	dp[0] = 0
	val_set = set(num2match.values())
	match2num = {v:max([int(key) for key, val in num2match.items() if val == v]) for v in val_set}
 
	for i in range(2, n + 1):
		for val in val_set:
			if i >= val and dp[i - val] > 0:
				tmp = match2num[val] * (10 ** len(str(dp[i - val]))) + dp[i - val]
				dp[i] = max(dp[i], tmp)
			elif i >= val and dp[i - val] == 0:
				tmp = match2num[val]
				dp[i] = max(dp[i], tmp)
	
	#print(num2match)
	#print(match2num)
	#print(dp)
	print(int(dp[n]))
 
if __name__ == '__main__':
	main()