#ifndef LOCAL
#define FAST_IO
#endif

// ============
#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#define OVERRIDE(a, b, c, d, ...) d
#define REP2(i, n) for (i32 i = 0; i < (i32)(n); ++i)
#define REP3(i, m, n) for (i32 i = (i32)(m); i < (i32)(n); ++i)
#define REP(...) OVERRIDE(__VA_ARGS__, REP3, REP2)(__VA_ARGS__)
#define PER(i, n) for (i32 i = (i32)(n) - 1; i >= 0; --i)
#define ALL(x) begin(x), end(x)

using namespace std;

using u32 = unsigned int;
using u64 = unsigned long long;
using i32 = signed int;
using i64 = signed long long;
using f64 = double;
using f80 = long double;

template <typename T>
using Vec = vector<T>;

template <typename T>
bool chmin(T &x, const T &y) {
    if (x > y) {
        x = y;
        return true;
    }
    return false;
}
template <typename T>
bool chmax(T &x, const T &y) {
    if (x < y) {
        x = y;
        return true;
    }
    return false;
}

#ifdef INT128

using u128 = __uint128_t;
using i128 = __int128_t;

istream &operator>>(istream &is, i128 &x) {
    i64 v;
    is >> v;
    x = v;
    return is;
}
ostream &operator<<(ostream &os, i128 x) {
    os << (i64)x;
    return os;
}
istream &operator>>(istream &is, u128 &x) {
    u64 v;
    is >> v;
    x = v;
    return is;
}
ostream &operator<<(ostream &os, u128 x) {
    os << (u64)x;
    return os;
}

#endif

[[maybe_unused]] constexpr i32 INF = 1000000100;
[[maybe_unused]] constexpr i64 INF64 = 3000000000000000100;
struct SetUpIO {
    SetUpIO() {
#ifdef FAST_IO
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
#endif
        cout << fixed << setprecision(15);
    }
} set_up_io;
// ============

#ifdef DEBUGF
#else
#define DBG(x) (void)0
#endif

i32 solve(array<i32, 5> pos) {
    sort(ALL(pos));
    DBG(pos);
    i32 cur = 5;
    i32 ans = 0;
    i32 it = 0;
    while (it < 5 && pos[it] < cur) {
        ++it;
    }
    while (it < 5) {
        i32 diff = 5 - it;
        i32 mv = (pos[it] + 1 - cur + diff - 1) / diff;
        ans += mv;
        cur += diff * mv;
        while (it < 5 && pos[it] < cur) {
            ++it;
        }
    }
    return ans;
}

int main() {
    i32 n, m;
    cin >> n >> m;
    Vec<i32> a(n * m), b(n * m);
    REP(i, n * m) {
        cin >> a[i] >> b[i];
        --a[i];
        --b[i];
    }
    Vec<Vec<i32>> idx(n, Vec<i32>(m));
    REP(i, n * m) {
        idx[a[i]][b[i]] = i;
    }
    i32 ans = INF;
    REP(i, m) {
        REP(j, n - 4) {
            array<i32, 5> pos;
            REP(k, 5) {
                pos[k] = idx[j + k][i];
            }
            chmin(ans, solve(pos));
        }
        {
            array<i32, 5> pos;
            pos[0] = idx[0][i];
            REP(k, 4) {
                pos[k + 1] = idx[n - 4 + k][i];
            }
            chmin(ans, solve(pos));
        }
    }
    cout << ans << '\n';
}