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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
map<int, int> n_match={{1,2}, {2,5}, {3,5}, {4,4}, {5,5}, {6,6}, {7,3}, {8,7}, {9,6}};

int main(){
  int N, M;cin>>N>>M;
  vi A;
  for (int i=0;i<M;++i){int a;cin>>a;A.push_back(a);}

  vi use_list(10, -1);
  for (int i=2;i<=7;++i){
    for (int m=0;m<M;++m){
      if(n_match[A[m]]==i) use_list[i]=max(use_list[i], A[m]);
    }
  }

  vvi dp(N+10);

  for (int i=0;i<N+10;++i){
    for (int j=0;j<10;++j){
      dp[i].push_back(-1);
    }
  }

  for (int i=0;i<=N;++i){
    for (int j=2;j<=7;++j){
      dp[i][j]++;dp[i][0]++;
      dp[i+j]=max(dp[i], dp[i+j]);
      dp[i][j]--;dp[i][0]--;
    }
  }

  for (int i=1;i<10;++i){
    for (int j=0;j<dp[N][i];++j){
      cout << 10-i;
    }
  }

  return 0;
}