Description:
You are given two integer numbers, $$$n$$$ and $$$x$$$. You may perform several operations with the integer $$$x$$$.
Each operation you perform is the following one: choose any digit $$$y$$$ that occurs in the decimal representation of $$$x$$$ at least once, and replace $$$x$$$ by $$$x \cdot y$$$.
You want to make the length of decimal representation of $$$x$$$ (without leading zeroes) equal to $$$n$$$. What is the minimum number of operations required to do that?
Input Format:
The only line of the input contains two integers $$$n$$$ and $$$x$$$ ($$$2 \le n \le 19$$$; $$$1 \le x < 10^{n-1}$$$).
Output Format:
Print one integer — the minimum number of operations required to make the length of decimal representation of $$$x$$$ (without leading zeroes) equal to $$$n$$$, or $$$-1$$$ if it is impossible.
Note:
In the second example, the following sequence of operations achieves the goal:
1. multiply $$$x$$$ by $$$2$$$, so $$$x = 2 \cdot 2 = 4$$$;
2. multiply $$$x$$$ by $$$4$$$, so $$$x = 4 \cdot 4 = 16$$$;
3. multiply $$$x$$$ by $$$6$$$, so $$$x = 16 \cdot 6 = 96$$$;
4. multiply $$$x$$$ by $$$9$$$, so $$$x = 96 \cdot 9 = 864$$$.