def inp() a=gets.chomp.split(" ").map(&:to_i)end 
def inpf() a=gets.chomp.split(" ").map(&:to_f)end
def inps() a=gets.chomp.split(" ")end  
def copy(a) Marshal.load(Marshal.dump(a)) end
def kaizyo(n)(n < 2)? 1 : (2..n).inject(:*) end
def scount(a) b = na(a.max+1); a.each{|n|b[n]+=1};return b end
def na(n=0,d=0) Array.new(n,d)end
def na2(n,m,d=0) Array.new(n){Array.new(m,d)}end
def na3(n,m,l,d=0) Array.new(n){Array.new(m){Array.new(l,d)}}end
n = inp[0]
tab = na(n)
c = 0
ind = na(n)
n.times do |i|
  tab[i] = inps
end
n.times do |i|
  n.times do |j|
    next if i == j
    if(tab[i][j] != "nyanpass")
      ind[j] = 1
    end
  end
end
puts (ind.count(0) != 1)? -1 : ind.index(0)+1