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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		try {
			int n = sc.nextInt();
			sc.nextLine();
			String s = sc.next();

			int first = s.indexOf('I');
			int end = s.lastIndexOf('I');

			if (first == -1) {
				System.out.println(0);
				return;
			}

			int x = 0 - first + 1;
			int max = x > 0 ? x : 0;
			for (int i = first + 1; i <= end; i++) {
				if (s.charAt(i) == 'I') {
					x++;
				} else {
					x--;
				}
				max = x > max ? x : max;
			}

			System.out.println(max);

		} finally {
			sc.close();
		}
	}
}