#include<bits/stdc++.h>
#include<atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using db = long double;
using ch = char;
using bl = bool;
using st = string;
using pll = pair<ll,ll>;
using psl = pair<st,ll>;
using vst = vector<st>;
using vch = vector<ch>;
using vvch = vector<vch>;
using vbl = vector<bl>;
using vvbl = vector<vbl>;
using vdb = vector<db>;
using vpll = vector<pll>;
using vvpll = vector<vpll>;
using vpsl = vector<psl>;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using vvvvi = vector<vvvi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vvvll = vector<vvll>;
using vvvvll = vector<vvvll>;
using vvvvvll = vector<vvvvll>;
template <class T> using pq = priority_queue<T>;
template <class T> using pqg = priority_queue<T,vector<T>,greater<T>>;
#define all(A) A.begin(),A.end()
#define sz(A) (ll)A.size()
#define pb(a) push_back(a)
#define mp(a,b) make_pair(a,b)
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define rrep(i,a,b) for(ll i=(ll)(a);i<=(ll)(b);i++)
#define drep(i,n) for(ll i=(ll)n-1; i>=0; i--)
#define drrep(i,a,b) for(ll i=(ll)a; i>=(ll)b; i--)

using mint = modint998244353;
// using mint = modint1000000007;
using vm = vector<mint>;
using vvm = vector<vm>; 
using vvvm = vector<vvm>;

const ll mod = 998244353;
// const ll mod = 1000000007;
const ll INF = 3e18;

template<class T> inline bool chmin(T &a, T b)
{
    if (a>b)
    {
        a=b;
        return true;
    }
    return false;
}

template<class T> inline bool chmax(T &a, T b)
{
    if (a<b)
    {
        a=b;
        return true;
    }
    return false;
}

ll gcd(ll a, ll b)
{
    if (a==0)return b;
    if (b==0)return a;
    ll c=a;
    while(a%b!=0)
    {
        c=a%b;
        a=b;
        b=c;
    }
    return b;
}

ll lcm(ll a,ll b){
    return a/gcd(a,b)*b;
}

ll Pow(ll a, ll n)
{
    ll res=1;
    while(n>0)
    {
        if(n%2==1)res*=a;
        a*=a;
        n/=2;
    }
    return res;
}

ll Pow(ll a, ll n, ll p)
{
    ll res=1;
    while(n>0)
    {
        a%=p;
        if(n%2==1)res*=a;
        a*=a;
        res%=p;
        n/=2;
    }
    return res;
}

void yn(bl ok)
{
    cout << (ok?"Yes\n":"No\n");
    return;
}

ll N,M,X[500][500];

ll solve(ll n, ll m)
{
    vll A;
    rep(i,5)A.pb(X[(n+i)%N][m]);
    sort(all(A));
    ll res=0,now=5,cnt=5;
    rep(i,5)
    {
        if(A[i]<=now)
        {
            cnt--;
            continue;
        }
        res+=(A[i]-now+cnt-1)/cnt;
        now+=(A[i]-now+cnt-1)/cnt*cnt;
        cnt++;
    }
    // cout << n << ' ' << m << ' ' << res << endl;
    return res;
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin>>N>>M;
    rep(i,N*M)
    {
        ll n,m;
        cin>>n>>m;
        n--,m--;
        X[n][m]=i+1;
    }
    ll ans=INF;
    rep(m,M)rrep(n,0,N-4)
    {
        chmin(ans,solve(n,m));
    }
    cout << ans << endl;
    return 0;
}