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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
 
namespace at
{
    class Program
    {
        static void Main(string[] args)
        {
            var x = 0;
            var N = int.Parse(Console.ReadLine());
            var s = Console.ReadLine();
            var a = new List<int>(){0};

            for (int i = 0; i < N; i++)
            {
                Console.WriteLine(s[i]);
                if((s[i]).ToString() == "I") a.Add(x = x + 1);
                if((s[i]).ToString() == "D") a.Add(x = x - 1);
            }
            Console.WriteLine(a.Max());
        }        
    }
}