package Mandatory3;
/*
@author Lucas Gramme
*/
import java.util.ArrayList;
import java.util.Scanner;

public class LetterLabyrinth2 {
    //Variables to save maze
    private int R, C;
    char[][] m;
    String[] input;
    //Starting point
    int sr = 0, sc = 0;
    //Track number of steps taken
    int move_count = 0;
    int node_left_in_layer = 1;
    int nodes_in_next_layer = 0;
    //Check if we have reached the end
    boolean reached_end = false;
    //Check if cell has been visited
    boolean visited[][] = new boolean[R][C];
    //North, south, east, west directions
    int[] dr = {-1, 1, 0, 0};
    int[] dc = {0, 0, 1, -1};
    //Queue
    ArrayList<Integer> rq = new ArrayList<>();
    ArrayList<Integer> cq = new ArrayList<>();

    public int solve(){
        rq.add(sr);
        cq.add(sc);
        visited[sr][sc] = true;
        while(rq.size() > 0){
            int r = rq.remove(0);
            int c = cq.remove(0);
            if(r == R-1 && c == C-1){
                move_count++;
                reached_end = true;
                break;
            }else{
                exploreNeighbours(r,c);
                node_left_in_layer--;
                if(node_left_in_layer == 0){
                    node_left_in_layer = nodes_in_next_layer;
                    nodes_in_next_layer = 0;
                    move_count++;
                }
            }
        }
        if(reached_end){
            return move_count;
        }else {
            return -1;
        }
    }

    private void exploreNeighbours(int r, int c) {
        for(int i = 0; i < 4; i++){
            int rr = r + dr[i];
            int cc = c + dc[i];
            //Skip out of bounds locations
            if(rr < 0 || cc < 0)continue;
            if(rr >= R || cc >= C)continue;
            //Skip visited cells
            if(visited[rr][cc])continue;
            //Skip invalid cells
            if(m[rr][cc] == m[r][c])continue;
            //Add neighbour to queue
            rq.add(rr);
            cq.add(cc);
            //Set neighbour to visited = true and add to next layer
            visited[rr][cc] = true;
            nodes_in_next_layer++;
        }
    }

    public void run(){
        Scanner scan = new Scanner(System.in);
        //Maze will be RxC
        R = C = scan.nextInt();
        input = new String[R];
        m = new char[R][C];
        visited = new boolean[R][C];
        for(int i = 0; i < R; i++){
            input[i] = scan.next();
            for(int j = 0; j < R; j++){
                m[i][j] = input[i].charAt(j);
            }
        }
        System.out.println(solve());
    }

    public static void main(String[] args) {
       new LetterLabyrinth2().run();
    }