import java.io.IOException;
import java.util.Arrays;
import java.util.InputMismatchException;

public class Main {
	int n;
	char[][] c;
	int min;

	void backtrack(int x, int y) {
		if (n <= y) {
			min = Math.min(min, check());
			return;
		}

		int nx = x + 1;
		int ny = y;
		if (n <= nx) {
			ny++;
			nx = ny;
		}

		if (c[y][x] != '-') {
			backtrack(nx, ny);
		} else {
			c[y][x] = 'o';
			c[x][y] = 'x';
			backtrack(nx, ny);
			c[y][x] = 'x';
			c[x][y] = 'o';
			backtrack(nx, ny);
			c[y][x] = c[x][y] = '-';
		}
	}

	int check() {
		class D implements Comparable<D> {
			int id, score, rank;

			public D(int id) {
				this.id = id;
				this.score = 0;
				this.rank = 0;
			}

			public int compareTo(D o) {
				return o.score - this.score;
			}
		}
		D[] d = new D[n];
		for (int i = 0; i < n; i++) {
			d[i] = new D(i);
		}
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < n; j++) {
				if (c[i][j] == 'o') {
					d[i].score++;
				}
			}
		}
		Arrays.sort(d);
		d[0].rank = 1;
		for (int i = 1; i < n; i++) {
			if (d[i].score == d[i - 1].score) {
				d[i].rank = d[i - 1].rank;
			} else {
				d[i].rank = d[i - 1].rank + 1;
			}
		}
		for (int i = 0; i < n; i++) {
			if (d[i].id == 0) {
				return d[i].rank;
			}
		}
		return -1;
	}

	void run() {
		MyScanner sc = new MyScanner();

		n = sc.nextInt();
		c = new char[n][];
		for (int i = 0; i < n; i++) {
			c[i] = sc.next().toCharArray();
		}
		min = 100;
		backtrack(0, 0);
		System.out.println(min);
	}

	public static void main(String[] args) {
		new Main().run();
	}

	public void mapDebug(int[][] a) {
		System.out.println("--------map display---------");
		for (int i = 0; i < a.length; i++) {
			for (int j = 0; j < a[i].length; j++) {
				System.out.printf("%3d ", a[i][j]);
			}
			System.out.println();
		}
		System.out.println("----------------------------" + '\n');
	}

	class MyScanner {
		int read() {
			try {
				return System.in.read();
			} catch (IOException e) {
				throw new InputMismatchException();
			}
		}

		boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		boolean isEndline(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

		int nextInt() {
			return Integer.parseInt(next());
		}

		int[] nextIntArray(int n) {
			int[] array = new int[n];
			for (int i = 0; i < n; i++)
				array[i] = nextInt();
			return array;
		}

		long nextLong() {
			return Long.parseLong(next());
		}

		long[] nextLongArray(int n) {
			long[] array = new long[n];
			for (int i = 0; i < n; i++)
				array[i] = nextLong();
			return array;
		}

		double nextDouble() {
			return Double.parseDouble(next());
		}

		double[] nextDoubleArray(int n) {
			double[] array = new double[n];
			for (int i = 0; i < n; i++)
				array[i] = nextDouble();
			return array;
		}

		String next() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		String[] nextStringArray(int n) {
			String[] array = new String[n];
			for (int i = 0; i < n; i++)
				array[i] = next();

			return array;
		}

		String nextLine() {
			int c = read();
			while (isEndline(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isEndline(c));
			return res.toString();
		}
	}
}