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.BufferedReader;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws Exception {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		String line = "";
		int strN = 2; // 文字列を何行受け取るか
		for (int i = 0; i < strN; i++) {
			line += br.readLine() + " ";
		}
		String[] param = line.split(" ");
		AtoZString(param);

	}

	static void AtoZString(String[] param) { //1行、文字列中のAからZまでの文字列で最大のものの文字数を出力[0]
		int max = 0;
		int count = 0;

		for(int i = 0; i < param[1].length(); i++){
			if(param[1].charAt(i) == 'I'){
				count++;
				if(max < count) max = count;
			} else if(param[1].charAt(i) == 'D'){
				count--;
			}
		}
		System.out.println(max);
	}
}