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 C++ (GCC 9.2.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
#define rep(i,n) for (int i=0; i<(n); ++i)
using namespace std;
typedef long long ll;
typedef pair<int,int> P;

const string M_INF="-";

int n,m,cost[]={0,2,5,5,4,5,6,3,7,6};
string dp[10010];

void chmax(string &s, string t){
  if(s.size()<t.size())s=t;
  if(s.size()==t.size())if(s<t)s=t;
}

int main(){
  cin>>n>>m;
  vector<int>a(m);
  rep(i,m)cin>>a[i];
  
  rep(i,10010)dp[i]=M_INF;
  dp[0]="";
  for(int i=0; i<=n; ++i){
    if(dp[i]==M_INF)continue;
    rep(j,m){
      chmax(dp[i+cost[a[j]]],dp[i]+char(a[j]+'0'));
    }
  }
  cout<<dp[n]<<endl;
}