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 5.4.1) (judge verdict: Runtime Error)

#include <stdio.h>
#include <stdlib.h>

typedef struct {
	char num;
	char use;
} Matchies;

Matchies mat[10];
char match[10]={63,63,63,63,63,63,63,63,63,63};
char m;
char ans[10000],ansNum=0;

int compareUse(const void *a,const void *b)
{
	return ((Matchies *)a)->use - ((Matchies *)b)->use;
}

int compareAns(const void *a,const void *b)
{
	return *(char *)a - *(char *)b;
}

void iniMatch()
{
	char i;
	for (i=0;i<10;i++) {
		mat[i].num = i;
		mat[i].use = match[i];
	}
}

char matching(int left)
{
	char i,j,ret;
	if (left<0) return 0;
	if (left==0) return 2;

	for (i=0;i<10;i++) {
		if (mat[i].use==63) break;

		ans[ansNum] = mat[i].num;
		ansNum++;
		ret = matching(left - mat[i].use);
		if (ret == 1) return 1;
		if (ret == 2) {
			if (mat[i].use==5 || mat[i].use==6) {
				j = i;
				while (1) {
					j++;
					if (mat[j].use != mat[i].use) break;
					if (mat[j].num > ans[ansNum-1]) ans[ansNum-1] = mat[j].num;
				}
			}
			return 1;
		}

		ansNum--;
	}

	return 0;
}

int main(void)
{
	int n,i;
	char *a,sub[10]={63,2,5,5,4,5,6,3,7,6};
	scanf("%d %hhd",&n,&m);
	a = (char *)malloc(sizeof(char) * m);
	for (i=0;i<m;i++) {
		scanf("%hhd",&a[i]);
	}
	for (i=0;i<m;i++) {
		match[a[i]] = sub[a[i]];
	}

	iniMatch();
	qsort(mat,10,sizeof(Matchies),compareUse);
	matching(n);

	qsort(ans,ansNum,sizeof(char),compareAns);

	for (i=ansNum-1;i>=0;i--) printf("%hhd",ans[i]);
	printf("\n");

	free(a);
	return 0;
}