#include<iostream>
#include<cstdio>
#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<cctype>
#include<cstdlib>
#include<algorithm>
#include<bitset>
#include<vector>
#include<list>
#include<deque>
#include<queue>
#include<map>
#include<set>
#include<stack>
#include<cmath>
#include<sstream>
#include<fstream>
#include<iomanip>
#include<ctime>
#include<complex>
#include<functional>
#include<climits>
#include<cassert>
#include<iterator>
#include<unordered_map>
using namespace std;
string a[102][102];
int n;
int main(){
	cin >> n;
	for (int i = 0; i < n; i++){
		for (int j = 0; j < n; j++){
			cin >> a[i][j];
		}
	}
	set<int> s;
	for (int i = 0; i < n; i++){
		bool ok = false;
		for (int j = 0; j < n; j++){
			if (i == j){
				continue;
			}
			if (a[j][i] == "nyanpass"){

			}
			else{
				ok = true;
			}
		}
		if (ok == false){
			s.insert(i + 1);
		}
	}
	if (s.size() == 1){
		cout << (*s.begin()) << endl;
	}
	else{
		puts("-1");
	}
	return 0;
}