#! ruby
# yukicoder My Practice
# author: Leonardone @ NEETSDKASU


N = gets.to_i

flag = [true] * N

N.times do |j|
	ai = gets.chomp.split
	N.times do |i|
		next if i == j
		flag[i] &= ai[i] == 'nyanpass'
	end
end

if flag.count(true) == 1
	puts flag.index(true).next
else
	puts '-1'
end