import java.util.Scanner;


public class Main_yukicoder239 {

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

        int n = sc.nextInt();
        
        String[][] a = new String[n][n];
        for (int i = 0; i < n; i++) {
        	for (int j = 0; j < n; j++) {
        		a[i][j] = sc.next();
        	}
        }

        int ret = -1;
        for (int i = 0; i < n; i++) {
        	boolean flag = true;
        	for (int j = 0; j < n; j++) {
        		if (j != i && !a[j][i].equals("nyanpass")) {
        			flag = false;
        			break;
        		}
        	}
        	if (flag && ret == -1) {
        		ret = i + 1;
        	} else if (flag && ret != -1) {
        		ret = -1;
        		break;
        	}
        }

        System.out.println(ret);
        
        sc.close();
    }
}