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.Linq;
using System.Collections.Generic;
using static System.Math;
using static System.Console;

namespace AtCoder
{
    class AtCoderrrrrr
    {
        static void Main(string[] args)
        {
            int N = int.Parse(ReadLine());
            string s = ReadLine();
            int ans = 0;
            int x = 0;
            for (int i = 0; i < N; i++)
            {
                if (s[i] == 'I')
                {
                    x++;
                }
                else
                {
                    x--;
                }
                if (x>ans)
                {
                    ans = x;
                }
            }
            WriteLine(ans);
        }
    }
}