A pile of stones

有一堆石子，给一个长度为$n$的操作序列，"-"表示取出一个石子，"+"表示放入一个石子，求这堆石子最后至少有几个

Vasya has a pile, that consists of some number of stones. $ n $ times he either took one stone from the pile or added one stone to the pile. The pile was non-empty before each operation of taking one stone from the pile. You are given $ n $ operations which Vasya has made. Find the minimal possible number of stones that can be in the pile after making these operations.

The first line contains one positive integer $ n $ — the number of operations, that have been made by Vasya ( $ 1 \leq n \leq 100 $ ). The next line contains the string $ s $ , consisting of $ n $ symbols, equal to "-" (without quotes) or "+" (without quotes). If Vasya took the stone on $ i $ -th operation, $ s_i $ is equal to "-" (without quotes), if added, $ s_i $ is equal to "+" (without quotes).

Print one integer — the minimal possible number of stones that can be in the pile after these $ n $ operations.

3
---

0

4
++++

4

2
-+

1

5
++-++

3

In the first test, if Vasya had $ 3 $ stones in the pile at the beginning, after making operations the number of stones will be equal to $ 0 $ . It is impossible to have less number of piles, so the answer is $ 0 $ . Please notice, that the number of stones at the beginning can't be less, than $ 3 $ , because in this case, Vasya won't be able to take a stone on some operation (the pile will be empty). In the second test, if Vasya had $ 0 $ stones in the pile at the beginning, after making operations the number of stones will be equal to $ 4 $ . It is impossible to have less number of piles because after making $ 4 $ operations the number of stones in the pile increases on $ 4 $ stones. So, the answer is $ 4 $ . In the third test, if Vasya had $ 1 $ stone in the pile at the beginning, after making operations the number of stones will be equal to $ 1 $ . It can be proved, that it is impossible to have less number of stones after making the operations. In the fourth test, if Vasya had $ 0 $ stones in the pile at the beginning, after making operations the number of stones will be equal to $ 3 $ .