local n = io.read("*n", "*l")
local s = io.read()
local ret, t = 0, {}
local org = false
for i = 1, n - 1 do
  local a = s:sub(i, i) == "A"
  local b = s:sub(i + 1, i + 1) == "A"
  if a and b then
    ret = ret + 1
  elseif a then
    t[i] = true
  elseif b then
    t[i + 1] = true
  else
    org = true
  end
end
if org then ret = ret + 1 end
for k, v in pairs(t) do ret = ret + 1 end
print(ret)