#include <map>
#include <set>
#include <list>
#include <cmath>
#include <ctime>
#include <deque>
#include <queue>
#include <stack>
#include <string>
#include <bitset>
#include <cstdio>
#include <limits>
#include <vector>
#include <climits>
#include <cstring>
#include <cstdlib>
#include <fstream>
#include <numeric>
#include <sstream>
#include <iostream>
#include <algorithm>
#include <iomanip>
#include <cctype>
using namespace std;
typedef long long ll;

int main()
{
	int n;
	string v[101][101];
	vector<int>ans;
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= n; j++)
		{
			cin >> v[i][j];
		}
	}
	for (int j = 1; j <= n; j++)
	{
		bool flag = true;
		for (int i = 1; i <= n; i++)
		{
			if (j!=i&&v[i][j] != "nyanpass")
			{
				flag = false;
				break;
			}
		}
		if (flag)ans.push_back(j);
		if (static_cast<int>(ans.size()) > 1)
		{
			cout << -1 << endl;
			return 0;
		}
	}
	if (static_cast<int>(ans.size()))cout << ans[0] << endl;
	else cout << -1 << endl;
	return 0;
}