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.*;
import java.util.*;
 
public class Main {
    private static boolean debug = false;
    private static boolean elapsed = false;
 
    private static PrintWriter _out = new PrintWriter(System.out);
    private static PrintWriter _err = new PrintWriter(System.err);
 
    private void solve(Scanner sc) {
        int n = sc.nextInt();
        sc.nextLine();
        String s = sc.next();
 
        int max = 0;
        int x = 0;
        for (int i = 0; i < n; ++i) {
            char ch = s.charAt(i);
            if (ch == 'I') {
                ++x;
            } else if (ch == 'D') {
                --x;
            }
            if (x > max) {
                max = x;
            }
        }
        _out.println(max);
    }
    private long C(long n, long r) {
        long res = 1;
        for (long i = n; i > n - r; --i) {
            res *= i;
        }
        for (long i = r; i > 1; --i) {
            res /= i;
        }
        return res;
    }
    private long P(long n, long r) {
        long res = 1;
        for (long i = n; i > n - r; --i) {
            res *= i;
        }
        return res;
    }
    /*
     * 10^10 > Integer.MAX_VALUE = 2147483647 > 10^9
     * 10^19 > Long.MAX_VALUE = 9223372036854775807L > 10^18
     */
    public static void main(String[] args) {
        long S = System.currentTimeMillis();
 
        Scanner sc = new Scanner(System.in);
        new Main().solve(sc);
        _out.flush();
 
        long G = System.currentTimeMillis();
        if (elapsed) {
            _err.println((G - S) + "ms");
        }
        _err.flush();
    }
}