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: Runtime Error)

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.IOException;
 
public class Main{
	public static void main(String[] args)throws IOException{
		BufferedReader br = new BufferedReader(
			new InputStreamReader(System.in));
		String[] input = br.readLine().split(" ");
		int size = Integer.parseInt(input[0]);
		String s = input[1];
		char[] arr = s.toCharArray();
 
		int x = 0;
		int max = 0;
 
		for(int i = 0; i < size; i++){
			char c = arr[i];
			if(c =='I'){
				x += 1;
			}else{
				x--;
			}
			max = Math.max(max,x);
		}
		System.out.println(max);
	}
}