#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<ll, ll> P;

#define EACH(i,a) for (auto& i : a)
#define FOR(i,a,b) for (ll i=(a);i<(b);i++)
#define RFOR(i,a,b) for (ll i=(b)-1;i>=(a);i--)
#define REP(i,n) for (ll i=0;i<(n);i++)
#define RREP(i,n) for (ll i=(n)-1;i>=0;i--)
#define debug(x) cout<<#x<<": "<<x<<endl
#define pb push_back
#define ALL(a) (a).begin(),(a).end()

const ll linf = 1e18;
const int inf = 1e9;
const double eps = 1e-12;
const double pi = acos(-1);

template<typename T>
istream& operator>>(istream& is, vector<T>& vec) {
	EACH(x,vec) is >> x;
	return is;
}
template<typename T>
ostream& operator<<(ostream& os, vector<T>& vec) {
	REP(i,vec.size()) {
		if (i) os << " ";
		os << vec[i];
	}
	return os;
}
template<typename T>
ostream& operator<<(ostream& os, vector< vector<T> >& vec) {
	REP(i,vec.size()) {
		if (i) os << endl;
		os << vec[i];
	}
	return os;
}

bool check(string s1, string s2) {
	return s1 == s2;

	if (s1.size() < s2.size()) return false;
	REP(i, s1.size()-s2.size()+1) {
		if (s2 == s1.substr(i, s1.size()-i)) return true;
	}
	return false;
}

int main() {
	std::ios::sync_with_stdio(false);
	std::cin.tie(0);
	int N; cin >> N;
	vector< vector<string> > v(N, vector<string>(N)); cin >> v;
	set<int> s;
	REP(i, N) {
		bool f = true;
		REP(j, N) {
			if (i != j && v[j][i] != "nyanpass") {
				f = false;
				break;
			}
		}
		if (f) {
			s.insert(i);
		}
	}
	if (s.size() == 0) {
		cout << -1 << endl;
	}
	else if (s.size() == 1) {
		cout << *s.begin()+1 << endl;
	}
	else {
		cout << -1 << endl;
	}
}