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 (gfortran v4.8.4) (judge verdict: Accepted)

program main
implicit none
integer :: i, j, k
integer :: n
character :: s*100

read(*,*) n
read(*,*) s(1:n)
j = 0
k = 0
do i = 1, n
   if( s(i:i) == 'I' ) then
      j = j + 1
   else
      j = j - 1
   end if
   if( j .ge. k ) then
      k = j
   end if
end do
write(*,'(i0)') k



end program main