let n = Int(readLine()!)!
var s = readLine()!.map{String($0)}
s.append("A")
var cnt = 0, f = true
for i in 0...(n-2){
	if s[i] == "A"{
		cnt += 1
	}else{
	  if f && s[i+1] == "B"{
	    cnt += 1
	    f = false
	  }else if s[i+1] == "A" && s[i+2] == "A"{
			cnt += 1
		}
	}
}
print(cnt)