n = gets.to_i
cnt = Array.new(n, 0)
num = 0
idx = -1
for j in 0..n-1
  a = gets.chomp.split(" ")
  for i in 0..n-1
    if a[i] == 'nyanpass' then
      cnt[i] += 1
    end
  end
end

for i in 0..n-1
  if cnt[i] == n-1 then
    idx = i
    num += 1
  end
end


if num == 1 then
  puts(idx + 1)
else
  puts(-1)
end