d = gets.to_i
c = gets.strip
c += gets.strip
a = Array.new
count = 0
(c.length - 1).times do |i|
    if c[i] == c[i + 1]
        count += 1
    else
        a.push(count + 1)
        count = 0
    end
end
a.push(count + 1)
alen = a.length
s = c[0]
if alen == 1
    if s == "o"
        puts a[0] + d
        exit
    else
        puts d
        exit
    end
end
max = 0
st = (s == "o") ? 0 : 1
st.step(alen - 1, 2) do |i|
	m1 = 0
	m2 = 0
	if i + 1 < alen
		diff = d - a[i + 1]
		if diff >= 0
			if i + 2 < alen
				m1 = a[i] + a[i + 1] + a[i + 2]
			else
				m1 = a[i] + d
			end
		else
			m1 = a[i] + d
		end
	else
		m1 = a[i] + d
	end
	if i - 1 >= 0
		diff = d - a[i - 1]
		if diff >= 0
			if i - 2 >= 0
				m2 = a[i] + a[i - 1] + a[i - 2]
			else
				m2 = a[i] + d
			end
		else
			m2 = a[i] + d
		end
	else
		m1 = a[i] + d
	end
	#print m1, " ", m2, "\n"
    if m1 > max
        max = m1
    end
	if m2 > max
		max = m2
	end
end
puts max