// #pragma GCC target("avx")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

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

#define rep(i,n) for(int i = 0; i < (int)n; i++)
#define FOR(n) for(int i = 0; i < (int)n; i++)
#define repi(i,a,b) for(int i = (int)a; i < (int)b; i++)
#define all(x) x.begin(),x.end()
//#define mp make_pair
#define vi vector<int>
#define vvi vector<vi>
#define vvvi vector<vvi>
#define vvvvi vector<vvvi>
#define pii pair<int,int>
#define vpii vector<pair<int,int>>

template<typename T>
void chmax(T &a, const T &b) {a = (a > b? a : b);}
template<typename T>
void chmin(T &a, const T &b) {a = (a < b? a : b);}

using ll = long long;
using ld = long double;
using ull = unsigned long long;

const ll INF = numeric_limits<long long>::max() / 2;
const ld pi = 3.1415926535897932384626433832795028;
const ll mod = 998244353;
int dx[] = {1, 0, -1, 0, -1, -1, 1, 1};
int dy[] = {0, 1, 0, -1, -1, 1, -1, 1};

#define int long long

void solve() {
    int n, m;
    cin >> n >> m;
    const int nm = n*m;
    vector<vector<int>> ids(n, vector<int>(m));
    vi num(nm), suit(nm);
    FOR(nm) {
        cin >> num[i] >> suit[i];
        --num[i];
        --suit[i];
        ids[num[i]][suit[i]] = i+1;
    }

    int ans = INF;

    rep(i, n-3) {
        rep(j, m) {
            vi cur;
            rep(k, 5) {
                cur.push_back(ids[(i+k)%n][j]);
            }
            sort(all(cur));

            int change = 0;            
            int removed = 0;

            rep(k, 5) {
                if(cur[k] <= removed) continue;
                else {
                    int ops = (cur[k]-removed+(4-k))/(5-k);
                    removed += ops*(5-k);
                    change += ops;
                }
            }

            chmin(ans, change-1);
        }
    }

    cout << ans << endl;
}

signed main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}