package main

import . "fmt"
import . "strings"

func main() {
	var n,s string
	Scan(&n,&s)
	b:=[]byte(s)
	var c int
	if Contains(s,"BB") {
		c++
	}
	for i,x:=range b[1:] {
		y:=b[i]
		if x=='A'||y=='A' {
			c++
		}
		if i+2<len(b) {
			z:=b[i+2]
			if y=='A'&&x!=y&&y!=z {
				c--
			}
		}
	}
	Println(c)
}