def holiday s
    s += 'x'
    tmp = ans = 0
    15.times{|i|
        if s[i] == 'o'
            tmp += 1
        else
            ans = [tmp, ans].max
            tmp = 0
        end
        }
    return ans
end

def sol d, s
    if d == 0
        return holiday(s)
    else
        ans = 0
        14.times{|i|
            if s[i] == 'x'
                s[i] = 'o'
                ans = [sol(d - 1, s), ans].max
                s[i] = 'x'
            end
            }
        return ans
    end
end 

d = gets.to_i
s = STDIN.map(&:chomp).join('')
p sol(d, s)