import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################

def solve(z):
    z = sorted(z)
    rest = 0
    cost = 0
    last = 0
    for i in range(5):
        rest += z[i] - last
        cost += rest // (5 - i)
        rest %= (5 - i)
        last = z[i] + 1
    return cost
n, m  = na()
a = []
b = [[-1] * m for i in range(n)]
for t in range(n * m):
    x, y = na()
    x -= 1
    y -= 1
    a.append((x, y))
    b[x][y] = t

ans = 10 ** 18
for i in range(n-3):
    for j in range(m):
        z = []
        for k in range(5):
            z.append(b[(i + k) % n][j])
        ans = min(solve(z), ans)

print(ans)