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.IOException;
import java.io.InputStreamReader;
import java.nio.charset.StandardCharsets;
import java.util.*;

public class Main {

    int[] inputArray;
    Set<String> set = new HashSet<>();
    int K;

    public static void main(String[] args) throws IOException {
        new Main().run();
    }

    void run() {
        Scanner sc = new Scanner(System.in);
        int x=0;
        int max=0;
        int n = sc.nextInt();
        char[] input = sc.next().toCharArray();

        for(char c: input){
            if(c == 'I'){
                x++;
            } else if(c == 'D'){
                x--;
            }

            max = Math.max(max, x);
        }

        System.out.println(max);
    }

    double manhattan(Ten point1, Ten point2){
        return Math.abs(point1.getX() - point2.getX()) + Math.abs(point1.getY() - point2.getY());
    }

    void substring(String s, int num){
        for(int i=1; i<=num; i++){
            if(i > K){
                break;
            }
            for(int j=0; j<num; j++){
                if(j + i-1 < num){
//                    System.out.println(s.substring(j, j+i));
                    set.add(s.substring(j, j+i));
                } else {
                    break;
                }
            }
        }
    }

    void permutation(String s, String ans){
        if(s.length() <= 1){
            System.out.println(ans + s);
        } else {
            for(int i=0; i<s.length(); i++){
                permutation(s.substring(0, i) + s.substring(i + 1), ans + s.charAt(i));
            }
        }
    }
}

class Ten{
    private int x;
    private int y;

    Ten(int x, int y){
        this.x = x;
        this.y = y;
    }

    public int getX() {
        return x;
    }

    public void setX(int x) {
        this.x = x;
    }

    public int getY() {
        return y;
    }

    public void setY(int y) {
        this.y = y;
    }
}