import sys
from collections import deque
input = sys.stdin.readline
dx = [-1, 1, 0, 0]
dy = [0, 0, -1, 1]
def bfs1(i, j):
global count
q = deque()
q.append([i, j])
vis[i][j] = True
arr[i][j] = count
while q:
x, y = q.popleft()
for k in range(4):
nx = x + dx[k]
ny = y + dy[k]
if 0 <= nx < n and 0 <= ny < n and arr[nx][ny] == 1 and not vis[nx][ny]:
vis[nx][ny] = True
arr[nx][ny] = count
q.append([nx, ny])
def bfs2(z):
global answer
dist = [[-1] * n for _ in range(n)]
q = deque()
for i in range(n):
for j in range(n):
if arr[i][j] == z:
q.append([i, j])
dist[i][j] = 0
while q:
x, y = q.popleft()
for i in range(4):
nx = x + dx[i]
ny = y + dy[i]
if nx < 0 or nx >= n or ny < 0 or ny >= n:
continue
if arr[nx][ny] > 0 and arr[nx][ny] != z:
answer = min(answer, dist[x][y])
return
if arr[nx][ny] == 0 and dist[nx][ny] == -1:
dist[nx][ny] = dist[x][y] + 1
q.append([nx, ny])
n = int(input())
arr = [list(map(int, input().split())) for _ in range(n)]
vis = [[False] * n for _ in range(n)]
count = 1
answer = sys.maxsize
for i in range(n):
for j in range(n):
if not vis[i][j] and arr[i][j] == 1:
bfs1(i, j)
count += 1
for i in range(1, count):
bfs2(i)
print(answer)