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 sample
    implicit none
    character(100)::s
    character(3)::ans
    integer(8) :: i,j,m,n,max
    integer(8),allocatable :: x(:),y(:)
  
    read(*,*)n
    read(*,*)s
    m=0
    max=0
    do i=1,n
        if(s(i:i) .eq. 'I')then
            m=m+1
            if(m>max)then
                max=m
            end if
        else
            m=m-1
        endif
    end do
    
  
    write(*,*)max
    stop
end program sample