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 AtcoderPractice
{
    class Program
    {
        static void Main(string[] args)
        {
            string ns = Console.ReadLine();
            string s = Console.ReadLine();
            int n = int.Parse(ns);
            int x = 0;
            int xMax = 0;
            for(int i = 0; i < n; i++)
            {
                if(s[i] == 'I')
                {
                    x++;
                    if(xMax < x)
                    {
                        xMax = x;
                    }
                }
                else
                {
                    x--;
                }
            }
            Console.WriteLine(xMax);
        }
    }
}