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 Go (1.6) (judge verdict: Accepted)

package main

import (
	"bufio"
	"fmt"
	"math"
	"os"
	"strconv"
)

var sc = bufio.NewScanner(os.Stdin)

func init() {
	sc.Split(bufio.ScanWords)
	sc.Buffer([]byte{}, math.MaxInt64)
}

func readString() string {
	sc.Scan()
	return sc.Text()
}

func readInt() int {
	sc.Scan()
	r, _ := strconv.Atoi(sc.Text())
	return r
}

func main() {
	n := readInt()
	s := readString()
	cnt, max := 0, 0
	for i := 0; i < n; i++ {
		switch string(s[i]) {
		case "I":
			cnt++
			if max < cnt {
				max = cnt
			}
		case "D":
			cnt--
		}
	}
	fmt.Println(max)
}