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Score : $200$ points

### Problem Statement

You have an integer variable $x$. Initially, $x=0$.

Some person gave you a string $S$ of length $N$, and using the string you performed the following operation $N$ times. In the $i$-th operation, you incremented the value of $x$ by $1$ if $S_i=$I, and decremented the value of $x$ by $1$ if $S_i=$D.

Find the maximum value taken by $x$ during the operations (including before the first operation, and after the last operation).

### Constraints

• $1≤N≤100$
• $|S|=N$
• No characters except I and D occur in $S$.

### Input

The input is given from Standard Input in the following format:

$N$
$S$

### Output

Print the maximum value taken by $x$ during the operations.

5
IIDID

### Sample Output 1

2

After each operation, the value of $x$ becomes $1$, $2$, $1$, $2$ and $1$, respectively. Thus, the output should be $2$, the maximum value.

7
DDIDDII

### Sample Output 2

0

The initial value $x=0$ is the maximum value taken by $x$, thus the output should be $0$.