N = gets.to_i
S = gets.chomp

checked = Hash.new
ans = 0

0.upto(N - 2) do |i|
  s = []
  s << i if S[i] == 'A'
  s << i + 1 if S[i + 1] == 'A'

  if not checked[s]
    checked[s] = true
    ans += 1
  end
end

puts ans