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.Scanner;

public class Main {

	private static final char INCREASE = 'I';
	private static final char DECREASE = 'D';

	public static void main(String[] args) {
		try (Scanner scanner = new Scanner(System.in)) {
			// n
			scanner.nextInt();
			char[] s = scanner.next().toCharArray();
			int max = 0, x = 0;
			for (char c : s) {
				switch (c) {
				case INCREASE:
					x++;
					max = Math.max(x, max);
					break;
				case DECREASE:
				default:
					x--;
					break;
				}
			}
			System.out.println(max);
		}
	}
}