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)

import sys
sys.setrecursionlimit(10**8)
from operator import itemgetter
#cost,value
matches = {1:2,2:5,3:5,4:4,5:5,6:6,7:3,8:7,9:6}
li = []
N,M = [int(x) for x in input().split()]
A = [int(x) for x in input().split()]

def dfs(n,num,cand):
    if(n>=len(li) or num+li[n][1]>N):
        return False
    if(num+li[n][1]==N):
        if(li[n][0] in cand):
            cand[li[n][0]]+=1
        else:
            cand[li[n][0]]=1
        return True
    for i in range(n,len(li)):
        if(dfs(i,num+li[n][1],cand)):
            if(li[n][0] in cand):
                cand[li[n][0]]+=1
            else:
                cand[li[n][0]]=1
            return True
    return False

for x in A:
    li+=[(x,matches[x])]
li.sort(key=itemgetter(1,0))
cand={}
dfs(0,0,cand)
ans = ''
for i in cand:
    ans = str(i)*cand[i]+ans

print(ans)