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.*;

public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    String s = sc.next();
    //nとstringを取得
    
    ArrayList<Integer> list = new ArrayList<>();
    int x = 0;
    //空のx,配列listを作成
    
    char[] chr;
    chr = s.toCharArray();
    //tocharArrayでstringをchar[n]の配列に
    
    for (int i=0; i<n; i++){
      if (chr[i]=='I'){
        x++;
        list.add(i, x);
      }else{
        x--;
        list.add(i, x);
      }//forでn回回す、Iだったらlist[i].add(x++)、Dだったらx--
    }
    Collections.sort(list);
    if(list.get(n-1)>0){
      System.out.println(list.get(n-1));
    }else{
      System.out.println(0);
    }
  }
}

//listをArrays.sort
//list[0]を表示