# input
n = gets.to_i
a = n.times.map{
     gets.split
    }

# solve
anser = -1
n.times.each{|i|
  if a.map{|b| b[i-1]}.inject(true){|result, str| result && (str == 'nyanpass' || str =='-') }
    if anser == -1
      anser = i
    else
      anser = -1
      break
    end
  end
}

print anser