Problem Description

JOI has $0$ or more of each of $3$ types of stamps: circle stamps, cross stamps, and circle-cross stamps. These are stamps that can print circle or cross marks on paper.

Using a circle stamp prints $1$ circle, and using a cross stamp prints $1$ cross. Using a circle-cross stamp prints a circle and a cross ($1$ of each) in a horizontal row, and by changing the orientation of the stamp, it can be printed either with the cross to the right of the circle or with the circle to the right of the cross.

JOI used each of the stamps he has exactly $1$ time in an appropriate order to print circles and crosses in a horizontal row on paper. The sequence of printed circles and crosses is represented by a string $S$. $S$ is a string of length $N$ consisting of O and X; if $S_i = $ O, it means that the $i$-th mark from the left among the marks printed by JOI is a circle, and if $S_i =$ X, it means that it is a cross ($1 \le i \le N$).

You do not know the number of stamps JOI has, but you know the sequence of circles and crosses printed by JOI. From the sequence of printed circles and crosses, find the maximum possible number of circle-cross stamps that JOI could have.

Constraints

• $1 \le N \le 100000 (= 10^5)$
• $S$ is a string of length $N$.
• Each character of $S$ is O or X.

Input / Output

Input
The input is given from Standard Input in the following format:
$N$
$S$

Output
Output the maximum possible number of circle-cross stamps that JOI could have.

Sample Input / Output

Sample Input 1

5
OXXOX

Sample Output 1

2

The marks printed by JOI are, in order from the left, circle, cross, cross, circle, cross. If JOI has $0, 1, 2$ circle stamps, cross stamps, and circle-cross stamps respectively, he can print the marks in this way by using the stamps in the following order:

• Use the $1$-st circle-cross stamp to print a circle and a cross in this order.
• To the right of this, use the $2$-nd circle-cross stamp to print a cross and a circle in this order.
• Finally, to the right of this, use the cross stamp to print a cross.

Since it is impossible for him to have $3$ or more circle-cross stamps, output $2$.

Sample Input 2

14
OXOXOXOXXOXOXO

Sample Output 2

7

Sample Input 3

10
OOOOOOOOOO

Sample Output 3

0