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.*;

public class Main{

    public static void main(String[] args) throws IOException{
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	String N_moji = br.readLine();
	int N = Integer.parseInt(N_moji);
	String S = br.readLine();
	int x_max = 0,i,x = 0;
	for(i = 0; i < N; i++){
	    if(S.charAt(i) == 'D'){
		x--;
	    }
	    else{
		x++;
		if(x_max <= x){
		    x_max = x;
		}
	    }
	}
	System.out.println(x_max);
    }
}