n = gets.chomp.to_i
an = [""] * n
ans = []
while i = gets
  s = i.chomp.split
  n.times{|i| an[i] += " "+s[i]}
end
n.times{|i|ans << an[i].split.count("nyanpass")}
p ans.count(ans.max) == 1 ? ans.count(ans.max) : -1