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: Wrong Answer)

package main

import(
	"fmt"
)

func main(){
	var x, n int
	var s string

	fmt.Scan(&n)
	fmt.Scan(&s)

	for _, c := range s {
		var r = calc(c, x)
		if x < r {
			x = r
		}
	}


	fmt.Println(x)
}

func calc(str rune, c int) int {
	if str == 'I' {
		c++
	}else if str == 'D' {
		c--
	}

	return c
}