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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.lang.IllegalArgumentException
import java.util.*

fun main(args: Array<String>) {
    val sc = Scanner(System.`in`)
    val n = sc.nextInt()
    val s = sc.next()
    println(answer052b(s))
}

fun answer052b(s: String): Int {
    var x = 0
    var answer = x

    s.forEach {
        answer = Math.max(x, answer)
        when (it) {
            'I' -> x++
            'D' -> x--
            else -> throw IllegalArgumentException("wrong args")
        }
        answer = Math.max(x, answer)
    }
    return answer
}