Problem:
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.

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.

Solution in Java (OpenJDK 11.0.6) (judge verdict: Accepted)

import java.util.*;
// warm-up
public class Main {

	static void solve() {
		Scanner sc = new Scanner(System.in);
		int max = Integer.MIN_VALUE, t=0;
		sc.nextInt();
		for (char ch : sc.next().toCharArray()) {
			t+=ch=='I' ? 1 : -1;
			max=(t>max) ? t : max;
		}
		System.out.println(Math.max(max, 0));
		sc.close();			
	}

	public static void main(String args[]) {
		solve();
	}

}