import java.util.*;
public class N2146 {

   static int input;
   static int[] dx = {-1,1,0,0};
   static int[] dy = {0,0,1,-1};
   static int answer=0;
   static int answer2=Integer.MAX_VALUE;
   static int flag;
   public static final ArrayList<Integer> list = new ArrayList<>();

   public static void main(String[] args) {
      // TODO Auto-generated method stub
      Scanner sc = new Scanner(System.in);

      input = sc.nextInt();
      int[][] array = new int[input][input];
      boolean[][] check = new boolean[input][input];
      boolean[][] check2 = new boolean[input][input];
      int[][] dist = new int[input][input];
      int[][] dist2 = new int[input][input];

      Queue<int[]> q = new LinkedList<int[]>();

      int count=0;
      //int answer =0;

      for(int i=0; i<input; i++) {
         for(int t=0; t<input; t++) {
            array[i][t] = sc.nextInt();
         }
      }

      //섬 영역 구하기
      for(int i=0; i<input; i++) {
         for(int k=0; k<input ; k++) {
            if(array[i][k]==1 && check[i][k]==false ) {
               bfs(array, count+=1, check, dist, i, k);
            }
         }
      }


      for(int i=0; i<input; i++) {
         for(int k=0; k<input ; k++) {
            if(dist[i][k]!=0) {
               q.offer(new int[] {i,k});
            }
         }
      }
      test( dist2, answer2, check2, dist,  q);

      for(int v : list) {
         if (answer2 > v) {
            answer2 = v;
         }
      }
//      System.out.println(list);
//
//      for(int i=0; i<input; i++) {
//         for(int k=0; k<input ; k++) {
//            System.out.print(dist2[i][k]);
//            if(k==input-1) System.out.println("");
//         }
//      }

      System.out.println(answer2);


   }

   static void bfs(int[][] array, int count, boolean[][] check, int[][] dist, int x, int y) {
      Queue<int[]> q = new LinkedList<int[]>();
      q.offer(new int[] {x,y});
      check[x][y] = true;
      dist[x][y] = count;

      while(!q.isEmpty()) {
         int[] head = q.poll();
         for(int i=0; i<4; i++) {
            int nx = head[0] + dx[i];
            int ny = head[1] + dy[i];

            if(nx>=0 && ny>=0 && nx<input && ny<input) {
               if(array[nx][ny]==1 && check[nx][ny] == false) {
                  bfs(array,count,check,dist,nx,ny);
               }
            }
         }
      }
   }

   static void test(int[][] array, int answer, boolean[][] check2, int[][] dist, Queue<int[]> q) {


      Loop : while(!q.isEmpty()) {
         int[] head = q.poll();
         for(int i=0; i<4; i++) {
            int nx = head[0] + dx[i];
            int ny = head[1] + dy[i];

            if(nx>=0 && ny>=0 && nx<input && ny<input) {
               if(dist[nx][ny]!=0 && dist[nx][ny] != dist[head[0]][head[1]]) {
                  list.add(array[nx][ny] + array[head[0]][head[1]]);
//                  System.out.println("nx : "+nx + "  ny" + ny + "  head  " + head[0] + "  hhh" + head[1]);
//                  System.out.println(array[nx][ny] +"    " + array[head[0]][head[1]]);
               }
               if(dist[nx][ny]==0 ) {
                  q.offer(new int[] {nx,ny});
                  dist[nx][ny]  = dist[head[0]][head[1]];
                  array[nx][ny] = array[head[0]][head[1]]+1;
                  //test(array,answer++,check2,dist,nx,ny);
               }


            }
         }
      }
   }

}