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 Rust (1.15.1) (judge verdict: Wrong Answer)

#[allow(unused_macros)]
macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        let mut next = || { iter.next().unwrap() };
        input_inner!{next, $($r)*}
    };
    ($($r:tt)*) => {
        let stdin = std::io::stdin();
        let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock()));
        let mut next = move || -> String{
            bytes
                .by_ref()
                .map(|r|r.unwrap() as char)
                .skip_while(|c|c.is_whitespace())
                .take_while(|c|!c.is_whitespace())
                .collect()
        };
        input_inner!{next, $($r)*}
    };
}

#[allow(unused_macros)]
macro_rules! input_inner {
    ($next:expr) => {};
    ($next:expr, ) => {};

    ($next:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };

    ($next:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = read_value!($next, $t);
        input_inner!{$next $($r)*}
    };
}

#[allow(unused_macros)]
macro_rules! read_value {
    ($next:expr, ( $($t:tt),* )) => {
        ( $(read_value!($next, $t)),* )
    };

    ($next:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($next, $t)).collect::<Vec<_>>()
    };

    ($next:expr, chars) => {
        read_value!($next, String).chars().collect::<Vec<char>>()
    };

    ($next:expr, bytes) => {
        read_value!($next, String).into_bytes()
    };

    ($next:expr, usize1) => {
        read_value!($next, usize) - 1
    };

    ($next:expr, $t:ty) => {
        $next().parse::<$t>().expect("Parse error")
    };
}

fn main() {
    input! {
        n: usize,
        m: usize,
        mut a: [usize; m],
    }

    let num = [0, 2, 5, 5, 4, 5, 6, 3, 7, 6];
    let mut nums = [None; 10];

    for n in a {
        nums[n] = Some(num[n]);
    }

    let mut dp = vec![None; n + 1];

    'outer: for i in 1..n + 1 {
        // dp loop
        for j in (1..10).rev() {
            // match loop
            if let Some(m) = nums[j] {
                //
                if i >= m {
                    // dp[i-m]
                    match dp[i - m] {
                        None => dp[i] = Some(j),
                        Some(x) => {
                            let mut acc = 0;

                            let mut digits = Vec::new();
                            let mut x = x;
                            while x > 0 {
                                digits.push(x % 10);
                                x /= 10;
                            }

                            let mut used = false;
                            for &y in digits.iter().rev() {
                                if y > m || used {
                                    acc = acc * 10 + y;
                                } else {
                                    acc = acc * 10 + m;
                                    acc = acc * 10 + y;
                                    used = true;
                                }
                            }

                            if !used {
                                acc = acc * 10 + m;
                            }
                            // println!("i = {}, j = {}, m = {}", i, j, m);
                            // println!("digits = {:?}", dp[i - m]);
                            // println!("acc = {:?}", acc);

                            dp[i] = Some(acc);
                        }
                    }
                    continue 'outer;
                }
            }
        }
    }
    if let Some(ans) = dp[n] {
        println!("{}", ans);
    } else {
        println!("{:?}", dp);
        panic!("none...?");
    }
}