package main

import . "fmt"
import . "strings"

func main() {
	var n,s string
	Scan(&n,&s)
	var c int
	if Contains(s,"BB") {
		c++
	}
	for _,x:=range Split(s,"B") {
		if len(x)>1 {
			c+=len(x)-1
		}
	}
	c+=Count(s,"AB")
	c+=Count(s,"BA")
	c-=Count(s,"BAB")
	Println(c)
}