def min(a,b); a < b ? a : b; end
def max(a,b); a > b ? a : b; end
  
N = gets.to_i
B = N.times.map { gets.chomp }
W = Array.new(N, 0)
Q = []

(0 ... N).each do |i|
  (i ... N).each do |j|
    if B[i][j] == 'o'
      W[i] += 1
    elsif B[i][j] == 'x'
      W[j] += 1
    elsif B[i][j] == '-'
      Q << [i, j]
    end
  end
end

def dfs(i)
  if i < Q.size
    a,b = Q[i]
    Q[i].map do |j| 
      W[j] += 1
      s = dfs(i + 1)
      W[j] -= 1
      s
    end.min
  else
    r = (0 ... N).group_by{|i| W[i] }
    return r.keys.sort.reverse.index{|t| r[t].include?(0) } + 1
  end
end

puts dfs(0)