#include <cstdio>
#include <algorithm>
using namespace std;
int n, k, ans = 0;
int a[1000];
int arr[1000];
bool used[1000];
inline bool check(int x)
{
	int p;
	while (x)
	{
		p = x % 10;
		if (p != 4 && p != 7) return false;
		x /= 10;
	}
	return true;
}
void dfs(int step, int last)
{
	if (step == k)
	{
		int flag = 1;
		for (int i = 0; i < k - 1 && flag; i++)
			if ((arr[i] == arr[i + 1]) && check(arr[i]))
				flag = 0;
		ans += flag;
	}
	else
		for (int i = last + 1; i < n; i++)
			if (!used[i])
			{
				used[i] = true;
				arr[step] = a[i];
				dfs(step + 1, i);
				used[i] = false;
			}
}
int main()
{
	freopen("lucky.in", "r", stdin);
	freopen("lucky.out", "w", stdout);
	scanf("%d%d", &n, &k);
	for (int i = 0; i < n; i++)
		scanf("%d", a + i);
	sort(a, a + n);
	dfs(0, -1);
	printf("%d", ans);
	return 0;
}