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).

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.

Constraints

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

Sample Input 1

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.

Sample Input 2

7
DDIDDII

Sample Output 2

0

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

见题面 Input 部分

见题面 Output 部分