from copy import *
import sys
input=lambda:sys.stdin.readline().strip()
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):
B=True;A='inf';mini=float(A);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 B
mini=float(A);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 B
return False
setup()
lo=0
hi=mx
while lo<hi:
mid=(lo+hi)//2
if check(mid):hi=mid
else:lo=mid+1
ans=lo
grid=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=ans
while lo<hi:
mid=(lo+hi)//2
if check(mid):hi=mid
else:lo=mid+1
print(min(ans,lo))
