#include <bits/stdc++.h>
using namespace std;
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) begin(v),end(v)
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
using ll = long long;
using pii = pair<int, int>;
constexpr ll INF = 1ll<<30;
constexpr ll longINF = 1ll<<60;
constexpr ll MOD = 1000000007;
constexpr bool debug = false;
//---------------------------------//

int main() {
	int N;
	cin >> N;
	vector nyanpass(N, vector(N, string()));
	REP(i, N) REP(j, N) cin >> nyanpass[i][j];
	vector<int> rentyon(N, true);
	REP(i, N) REP(j, N) if (i != j) rentyon[j] &= nyanpass[i][j] == "nyanpass";
	int s = accumulate(ALL(rentyon), 0);
	if (s == 1) cout << (max_element(ALL(rentyon)) - rentyon.begin() + 1) << endl;
	else puts("-1");
}