#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main(){
    int n, m; cin >> n >> m;
    vector<int> a(n*m), c(n*m);
    for(int i = 0; i < n*m; i++){
        cin >> a[i] >> c[i];
        a[i]--; c[i]--;
    }

    vector<vector<int>> t(n, vector<int>(m));
    for(int i = 0; i < n*m; i++){
        t[a[i]][c[i]] = i;
    }

    int ans = 1 << 30;
    for(int i = 0; i+3 < n; i++){
        for(int j = 0; j < m; j++){
            vector<int> tm;
            for(int k = 0; k < 5; k++){
                tm.emplace_back(t[(i+k)%n][j]);
            }
            sort(tm.begin(), tm.end());

            int res = 0;
            for(int k = 0, l = 5; k < 5; k++){
                if(tm[k] < l) continue;
                int x = (tm[k]+(5-k)-l)/(5-k);
                res += x;
                l += x*(5-k);
            }
            ans = min(ans, res);
        }
    }
    cout << ans << endl;
    return 0;
}