#define _CRT_SECURE_NO_WARNINGS
#pragma comment(linker, "/STACK:66777216")
#include <iostream>
#include <cstdio>
#include <cmath>
#include <vector>
#include <ctime>
#include <map>
#include <set>
#include <string>
#include <queue>
#include <deque>
#include <cassert>
#include <cstdlib>
#include <bitset>
#include <algorithm>
#include <string>
#include <list>
#include <fstream>
#include <sstream>
#include <unordered_set>
using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;

#define foreach(i, c) for(__typeof((c).begin()) i = (c).begin(); i != (c).end(); ++i)
#define forn(i, n) for (int i = 0; i < (int)n; i++)
#define fornn(i, q, n) for (int i = q; i < (int)n; i++)
#define mp make_pair
#define pk push_back
#define all(v) v.begin(), v.end()
#define times clock() * 1.0 / CLOCKS_PER_SEC

#define TASK "selfdual"

const double EPS = 1e-7;

const ll inf = (ll)2e9 + 7;
const ll LINF = (ll)9e18 + 7;
const ll MM = (ll)1e9 + 7;

int solve();

int main()
{
#ifdef _DEBUG
	freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
#else
	//freopen(TASK".in", "r", stdin), freopen(TASK".out", "w", stdout);
	//freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout), freopen("test.txt", "w", stderr);
#endif
	solve();
	return 0;
}
int a[3000][3000];
int l[100007];


int solve() {
	l[1] = 0;
 	fornn(i, 2, (int)1e5)
		l[i] = l[i / 2] + 1;
	l[0] = l[1] = 1;
	int n, m;
	cin >> n >> m;
	if (n == 1) {
		cout << 0;
		return 0;
	}
	vector<vector<int> > w(n, vector<int>(m));
	set<int> q;
	int mx = 0;
	forn(i, n) {
		forn(j, m) {
			cin >> w[i][j];
			mx = max(mx, w[i][j]);
		}
	}
	if (mx <= 200 && n > 40) {
		int k = (l[n] + 1) / 2;
		char t1[10007][207];
		forn(i, n) {
			forn(j, m) {
				t1[i][w[i][j]] = true;
			}
		}
		forn(i, 1 << k) {
			forn(j, 1 << k) {
				forn(l, k)
					a[i][j] += ((j & (1 << l)) > 0) * ((i & (1 << l)) > 0);
			}
		}
		vector<vector<int> > e(n);
		forn(i, n) {
			for (int r = 0; r < mx; r += k) {
				int crnt = 0;
				for (int dx = r; dx < r + k && dx < mx; dx++) {
					if (t1[i][dx])
						crnt += (1 << (dx - r));
				}
				e[i].pk(crnt);
			}
		}
		int an = 0;
		forn(i, n) {
			forn(j, i) {
				int crnt = 0;
				int cnt = 0;
				for (int l = 0; l < mx; l += k) {
					crnt += a[e[i][cnt]][e[j][cnt]];
					cnt++;
				}
				an = max(an, crnt);
			}
		}
		cout << an + 1;
		return 0;
	}
	forn(i, n) {
		forn(j, m) {
			q.insert(w[i][j]);
		}
	}

	int cnt = 0;
	map<int, int> MyFirstMap;
	for (auto i : q) {
		MyFirstMap[i] = cnt;
		cnt++;
	}
	vector<vector<char> > t(n, vector<char>(q.size(), false));
	forn(i, n) {
		forn(j, m) {
			t[i][MyFirstMap[w[i][j]]] = true;
		}
	}
	int k = l[n];
	forn(i, 1 << k) {
		forn(j, 1 << k) {
			forn(l, k)
				a[i][j] += ((j & (1 << l)) > 0) * ((i & (1 << l)) > 0);
		}
	}
	vector<vector<int> > e(n);
	forn(i, n) {
		for (int r = 0; r < q.size(); r += k) {
			int crnt = 0;
			for (int dx = r; dx < r + k && dx < q.size(); dx++) {
				if (t[i][dx])
					crnt += (1 << (dx - r));
			}
			e[i].pk(crnt);
		}
	}
	int an = 0;
	forn(i, n) {
		forn(j, i) {
			int crnt = 0;
			int cnt = 0;
			for (int l = 0; l < q.size(); l += k) {
				crnt += a[e[i][cnt]][e[j][cnt]];
				cnt++;
			}
			an = max(an, crnt);
		}
	}
	cout << an + 1;
	return 0;
}