import sys
read=sys.stdin.buffer.read
readline=sys.stdin.buffer.readline
readlines=sys.stdin.buffer.readlines

n, m=map(int, readline().split())
c=[[[] for _ in range(n)] for _ in range(m)]
for i in range(m):
    for j in range(n):
        c[i][j]=list(map(int, readline().split()))
ans=2*n
import itertools
def myon(d):
    res=[set() for i in range(2*n+2)]
    for i, di in enumerate(d):
        res[i]=set(di)
    for j in range(n):
        for i in range(n):
            res[j+n].add(d[i][j])
    for i in range(n):
        res[2*n].add(d[i][i])
        res[2*n+1].add(d[i][n-1-i])
    return res
s=[myon(ci) for ci in c]
for si, sj in itertools.combinations(s, 2):
    for di, dj in itertools.product(si, sj):
        ans=min(ans, len(di|dj))
print(ans-1)