import java.util.Scanner;

public class No_239 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		String[][] greetingList = new String[a][a];

		for (int i = 0; i < greetingList.length; i++) {
			for (int j = 0; j < greetingList.length; j++) {
				greetingList[i][j] = sc.next();
			}
		}

		int sum = 0;
		int renchonNumber = 0;
		boolean renchon = false;
		Loop: for (int i = 0; i < greetingList.length; i++) {
			for (int j = 0; j < greetingList.length; j++) {
				if (i == j) {
					continue;
				}
				if (!greetingList[j][i].equals("nyanpass")) {
					continue Loop;
				}

			}
			sum++;
			renchonNumber = i + 1;
			renchon = true;
			if (sum > 1) {
				renchon = false;
				break;
			}
		}

		if (renchon) {
			System.out.println(renchonNumber);
		} else {
			System.out.println(-1);
		}

	}
}