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.io.IOException;
import java.util.ArrayList;
import java.util.Scanner;

class Main {
	public static void main(String args[]) throws IOException {
		@SuppressWarnings("resource")
		Scanner cin = new Scanner(System.in);
		ArrayList<String> inLines = new ArrayList<String>();
		for (; cin.hasNext();) {
			inLines.add(cin.nextLine());
		}
		Solver solver = new Solver();
		solver.solve(inLines);
	}
}

class Solver {

	public void solve(ArrayList<String> inLines) {
		int N = Integer.parseInt(inLines.get(0));
		String str = inLines.get(1);
		int maxX = 0;
		int x = 0;
		for (int i = 0; i < N; i++) {
			if (str.charAt(i) == 'I')
				x++;
			else if (str.charAt(i) == 'D')
				x -= 1;
			if (x > maxX)
				maxX = x;
		}
		System.out.println(maxX);
	}
}