from copy import *
n,m = map(int, input().split())
grid = [list(map(int, input().split()))for i in range(n)]
grid2 = [[0 for i in range(m)]for i in range(n)]
mx = -1
for i in range(n):
for j in range(m):
mx = max(mx, grid[i][j])
grid2[i][j] = grid[n-i-1][m-j-1]
minmaxl = [[1000000000 for i in range(m)]for i in range(n)]
minmaxr = [[1000000000 for i in range(m)]for i in range(n)]
def setup():
for i in range(n-1,-1,-1):
minmaxl[i][0] = grid[i][0]
for j in range(1,m):
minmaxl[i][j] = min(minmaxl[i][j-1], grid[i][j])
if i != n-1:
for j in range(m):
minmaxl[i][j] = min(minmaxl[i][j], minmaxl[i+1][j])
for i in range(n-1,-1,-1):
minmaxr[i][m-1] = grid[i][m-1]
for j in range(m-2,-1,-1):
minmaxr[i][j] = min(minmaxr[i][j+1], grid[i][j])
if i != n-1:
for j in range(m-1,-1,-1):
minmaxr[i][j] = min(minmaxr[i][j], minmaxr[i+1][j])
def check(a):
mini = float("inf")
maxi = -1
for i in range(n):
for j in range(m):
if mx - minmaxl[i][j] > a:
mini = min(mini, grid[i][j])
maxi = max(maxi, grid[i][j])
if maxi - mini <= a:
return True
mini = float("inf")
maxi = -1
for i in range(n):
for j in range(m):
if mx - minmaxr[i][j] > a:
mini = min(mini, grid[i][j])
maxi = max(maxi, grid[i][j])
if maxi - mini <= a:
return True
return False
setup()
lo = 0
hi = 10000000000
while (lo<hi):
mid = (lo+hi)//2
if check(mid):
hi = mid
else:
lo = mid+1
ans = lo
grid = deepcopy(grid2)
minmaxl = [[1000000000 for i in range(m)]for i in range(n)]
minmaxr = [[1000000000 for i in range(m)]for i in range(n)]
setup()
lo = 0
hi = 10000000000
while (lo<hi):
mid = (lo+hi)//2
if check(mid):
hi = mid
else:
lo = mid+1
print(min(ans,lo))
