import java.util.*;
import java.io.*;
import java.awt.geom.*;
import java.math.*;

public class No0239 {
	
	static final Scanner in = new Scanner(System.in);
	static final PrintWriter out = new PrintWriter(System.out,false);

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

		int ans = -2;

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

			if (f) {
				if (ans == -2) {
					ans = i+1;
				}else {
					ans = -1;
				}
			}
		}

		out.println(ans < 0 ? "-1" : ans);
	}

	public static void main(String[] args) {
		long start = System.currentTimeMillis();

		solve();
		out.flush();

		long end = System.currentTimeMillis();
		//trace(end-start + "ms");
		in.close();
		out.close();
	}

	static void trace(Object... o) { System.out.println(Arrays.deepToString(o));}
}