import std.algorithm, std.array, std.container, std.range, std.bitmanip;
import std.numeric, std.math, std.bigint, std.random, core.bitop;
import std.string, std.regex, std.conv, std.stdio, std.typecons;

void main()
{
  auto n = readln.chomp.to!size_t;
  auto aij = iota(n).map!(_ => readln.split.array).array;

  size_t[] r;
  foreach (i; 0..n) {
    auto ai = aij.map!(ai => ai[i]).array;
    if ((ai[0..i] ~ ai[i+1..n]).all!(a => a == "nyanpass"))
      r ~= i;
  }

  if (r.length == 1)
    writeln(r.front + 1);
  else
    writeln(-1);
}