#include <bits/stdc++.h>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;
typedef long double ld;
int dx[8] = { 1, 0, -1, 0, 1, 1, -1, -1 }, dy[8] = { 0, 1, 0, -1, 1, -1, 1, -1 };
const long long mod = 998244353;
const ll inf = 1LL << 60;
const int INF = 5e8;

int main()
{
    int n, m;
    cin >> n >> m;
    vector<vector<int>> v(n, vector<int>(m));

    for (int i = 0; i < n * m; i++) {
        int a, b;
        cin >> a >> b;
        a--;
        b--;
        if (i < 5)
            continue;
        v[a][b] = i - 4;
    }

    int ans = INF;
    for (int j = 0; j < m; j++) {
        for (int i = 0; i < n - 3; i++) {
            int ret = 0;
            vector<int> vec;
            for (int k = 0; k < 5; k++)
                vec.push_back(v[(i + k) % n][j]);
            sort(vec.begin(), vec.end());
            int cnt = 5;
            int pos = 0;
            while (cnt) {
                if (vec[5 - cnt] <= pos) {
                    cnt--;
                    continue;
                }
                int step = (vec[5 - cnt] - pos - 1) / cnt + 1;
                ret += step;
                pos += cnt * step;
                cnt--;
            }
            ans = min(ans, ret);
        }
    }
    cout << ans << endl;
}