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;

namespace B_009_52
{
    internal class Program
    {
        private static void Main(string[] args)
        {
    
            new Logic_B().Start();//
       
        }

        public class Logic_B
        {
            public void Start()
            {
                var num = Console.ReadLine();
                var str = Console.ReadLine();

                var x = 0;
                var max = 0;
                for (int i = 0; i < str.Length; i++)
                {
                    if (str[i] == 'I')
                    {
                        x++;
                    }

                    if (str[i] == 'D')
                    {
                        x--;
                    }
                    max = Math.Max(x, max);
                }
                Console.WriteLine(max);
            }
        }

    }
}