#include <string>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#include <numeric>
#include <bitset>
#include <list>
#include <stdexcept>
#include <functional>
#include <utility>
#include <iomanip>
#include <ctime>
#include <valarray>
#include <iostream>
#include <sstream>
#include <fstream>
using namespace std;
typedef long long LL;
typedef unsigned long long ULL;
#define MEM(a,b) memset((a),(b),sizeof(a))
const LL INF = 1e9 + 7;
const int N = 2e2 + 10;
set<string> s[N];
int main()
{
	//freopen("input.txt", "r", stdin);
	//freopen("output.txt", "w", stdout);
	int n;
	cin >> n;
	for (int i = 1; i <= n; i++)
	{
		for (int j = 1; j <= n; j++)
		{
			string str;
			cin >> str;
			if (i == j) continue;
			s[j].insert(str);
		}
	}
	vector<int> ans;
	for (int i = 1; i <= n; i++)
	{
		if (s[i].size() > 1) continue;
		if (*s[i].begin() == "nyanpass")
			ans.push_back(i);
	}
	if (ans.size() != 1) puts("-1");
	else printf("%d\n", ans[0]);
	return 0;
}