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 C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;

static class Program
{
    static void Main(string[] args)
    {
        //入力
        var N = int.Parse(Console.ReadLine());
        var S = Console.ReadLine().ToCharArray();

        var q = new Queue<char>();
        var list = new List<int>(){0};
        var x = 0;
        foreach(var c in S){
            q.Enqueue(c);
        }
        
        //処理
        for(var i = 0; i < N; i++){
            list.Add(q.Dequeue() == 'I' ? ++x : --x);
        }
        
        

        //出力
        Console.WriteLine(list.Max());
    }
}