#include <bits/stdc++.h>
#include <x86intrin.h>
using namespace std;
using namespace numbers;



int main(){
	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(ios::badbit | ios::failbit);
	int n, m;
	cin >> n >> m;
	vector<array<int, 2>> a(n * m);
	vector pos(n, vector<int>(m));
	for(auto i = 0; i < n * m; ++ i){
		cin >> a[i][0] >> a[i][1], -- a[i][0], -- a[i][1];
		pos[a[i][0]][a[i][1]] = i;
	}
	int res = numeric_limits<int>::max();
	for(auto xs = 0; xs + 5 <= n + 1; ++ xs){
		for(auto y = 0; y < m; ++ y){
			array<int, 5> p;
			for(auto dx = 0; dx < 5; ++ dx){
				p[dx] = pos[(xs + dx) % n][y];
			}
			ranges::sort(p);
			int last = -1, cur = -1;
			for(auto pick = 0; pick < 5; ++ pick){
				int i = p[pick], jump = 5 - pick;
				cur += (i - last + jump - 1) / jump;
				last += (i - last + jump - 1) / jump * jump;
			}
			res = min(res, cur);
		}
	}
	cout << res << "\n";
	return 0;
}

/*

*/

////////////////////////////////////////////////////////////////////////////////////////
//                                                                                    //
//                                   Coded by Aeren                                   //
//                                                                                    //
////////////////////////////////////////////////////////////////////////////////////////