Decomposition of a Number

Decompose the given natural number N into a sum of k natural numbers a_1, a_2, ..., a_k such that the sum of the digits of all these numbers, s(a_1) + s(a_2) + ... + s(a_k), equals the given natural number S. Additionally, the number of addends k should be minimized. Here, s(X) represents the sum of the digits in the decimal form of the natural number X.

Input

The first line contains an integer N (1 ≤ N ≤ 10^12), and the second line contains an integer S (1 ≤ S ≤ 10^12).

Output

Output an integer representing the minimal number of addends needed for the required decomposition. If no such decomposition exists where the sum of the digits of the addends equals S, output -1.

Examples