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: Accepted)

#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;

#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))
#define MOD (1000000007)
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1}; // 移動方向

int n,m;
int a[10];
const string MINUSINF = "-";
string dp[10100];

void input(){
    cin >> n >> m;
    for(int i=0;i<m;i++) cin >> a[i];
}

void chmax(string &a, string b){
    if(a == MINUSINF) a = b;
    else if (a.size() < b.size()) a = b;
    else if (a.size() == b.size()){
        if(a < b) a = b;
    }
}

int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    input();
    int num[10] = {2,5,5,4,5,6,3,7,6};
    for(int i=0;i<10100;++i) dp[i] = MINUSINF;
    dp[0] = "";
    for(int i=0;i<=n;++i){
        if(dp[i] == MINUSINF) continue;
        for(int j=0;j<m;++j) chmax(dp[i+num[a[j]-1]], dp[i] + to_string(a[j]));
    }
    cout << dp[n] << endl;
    return 0;
}