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 Fortran (GNU Fortran 9.2.1) (judge verdict: Accepted)

program prob2
    implicit none
    character(105) :: s
    integer :: n, i, ans, anss
    read(*,*) n, s
    ans = 0
    anss = 0
    do i = 1, n
        if(s(i:i) == 'I')then
            ans = ans + 1
        else 
            ans = ans - 1
        end if
        anss = max(anss, ans)
    end do
    write(*,*) anss

    stop
contains
end program prob2