class BIT():
    def __init__(self,n,mod=0):
        self.BIT = [0]*(n+1)
        self.num = n
        self.mod = mod

    """
    return A[1] + A[2] + ... A[idx] in O(log n)
    """
    def query(self,idx):
        res_sum = 0
        mod = self.mod
        while idx > 0:
            res_sum += self.BIT[idx]
            if mod:
                res_sum %= mod
            idx -= idx&(-idx)
        return res_sum

    """
    A[idx] += in O(log n)
    """
    def update(self,idx,x):
        mod = self.mod
        while idx <= self.num:
            self.BIT[idx] += x
            if mod:
                self.BIT[idx] %= mod
            idx += idx&(-idx)
        return

import sys,random,bisect
from collections import deque,defaultdict
from heapq import heapify,heappop,heappush
from itertools import permutations
from math import log,gcd

input = lambda :sys.stdin.readline()
mi = lambda :map(int,input().split())
li = lambda :list(mi())

M,K = mi()
A = li()

A = [a for a in A]

B = [[] for i in range(M)]
for i in range(M*K):
    B[A[i]%M].append(i)
for i in range(M):
    B[i].sort()

init = []
for j in range(K):
    for i in range(M):
        init.append(B[i][j])

fw = BIT(M*K)
tmp_inv = 0
for i in range(M*K):
    tmp_inv += i - fw.query(init[i])
    fw.update(init[i]+1,1)

C = [[0 for j in range(K)] for i in range(M)]
for j in range(K):
    tmp = [i for i in range(M)]
    tmp.sort(key=lambda i:B[i][j])
    
    for i in range(M):
        C[tmp[i]][j] = (M-1-i) - i

res = tmp_inv
for i in range(M):
    tmp_inv += sum(C[i])
    res = min(res,tmp_inv)

print(res)