Wrong Subtraction

已知一个数 $n$ ，你要对它进行 $k$ 次操作。对于每一次操作，如果 $n$ 的最后一位数字不为零，则将它减1，否则将它除以10（即删除最后一位数字）。 给出初始时的数 $n$ 和操作次数 $k$ ，求操作 $k$ 次后的结果。 保证结果是正整数。 感谢@bcr_233 提供的翻译

Little girl Tanya is learning how to decrease a number by one, but she does it wrong with a number consisting of two or more digits. Tanya subtracts one from a number by the following algorithm: - if the last digit of the number is non-zero, she decreases the number by one; - if the last digit of the number is zero, she divides the number by 10 (i.e. removes the last digit). You are given an integer number $ n $ . Tanya will subtract one from it $ k $ times. Your task is to print the result after all $ k $ subtractions. It is guaranteed that the result will be positive integer number.

The first line of the input contains two integer numbers $ n $ and $ k $ ( $ 2 \le n \le 10^9 $ , $ 1 \le k \le 50 $ ) — the number from which Tanya will subtract and the number of subtractions correspondingly.

Print one integer number — the result of the decreasing $ n $ by one $ k $ times. It is guaranteed that the result will be positive integer number.

512 4

50

1000000000 9

1

The first example corresponds to the following sequence: $ 512 \rightarrow 511 \rightarrow 510 \rightarrow 51 \rightarrow 50 $ .