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

void Read(int &val) {
	val = 0; char c;
	do { c = getchar(); } while (!isdigit(c));
	while (isdigit(c)) { val = val * 10 + c - '0'; c = getchar(); }
}

typedef pair<int, int> ii;
struct data {
	int u, v, x, y, val;
	data() {}; data(int u, int v, int x, int y, int val) : u(u), v(v), x(x), y(y), val(val) {};
};

const int N = 1004;
int n, a[N][N];

int h[4] = { -1, 0, 1, 0 }, c[4] = { 0, -1, 0, 1 };
int numVer, ver[N][N][5];
data Edge[2*N*N];
vector<int> adj[2*N*N];

void Build_Graph() {
	for (int u = 1; u <= n; ++u) for (int v = 1; v <= n; ++v) {
		for (int dir = 0; dir < 4; ++dir) {
			int x = u + h[dir], y = v + c[dir];
			if (x < 1 || x > n || y < 1 || y > n) continue;
			int rDir = (dir + 2) % 4;
			if (ver[x][y][rDir] != 0) ver[u][v][dir] = ver[x][y][rDir];
			else {
				ver[u][v][dir] = ++numVer;
				Edge[numVer] = data(u, v, x, y, abs(a[u][v] - a[x][y]));
			}
		}
	}

	for (int i = 1; i <= numVer; ++i) {
		int u = Edge[i].u, v = Edge[i].v;
		for (int dir = 0; dir < 4; ++dir) {
			int x = u + h[dir], y = v + c[dir];
			if (x < 1 || x > n || y < 1 || y > n) continue;
			if (x == Edge[i].x && y == Edge[i].y) continue;
			int Next = ver[u][v][dir];
			if ( abs(a[u][v] - a[x][y]) == Edge[i].val ) adj[i].push_back(Next);
		}

		int x = Edge[i].x, y = Edge[i].y;
		for (int dir = 0; dir < 4; ++dir) {
			int u = x + h[dir], v = y + c[dir];
			if (u < 1 || u > n || v < 1 || v > n) continue;
			if (u == Edge[i].u && v == Edge[i].v) continue;
			int Next = ver[x][y][dir];
			if ( abs(a[u][v] - a[x][y]) == Edge[i].val ) adj[i].push_back(Next);
 		}
	}
}

bool vis[2*N*N], ok[N][N];
vector<ii> vec;

void DFS(int u) {
	vis[u] = true;
	int tmpX = Edge[u].u, tmpY = Edge[u].v;
	if (!ok[tmpX][tmpY]) {
		vec.push_back(ii(tmpX, tmpY));
		ok[tmpX][tmpY] = true;
	}
	tmpX = Edge[u].x, tmpY = Edge[u].y;
	if (!ok[tmpX][tmpY]) {
		vec.push_back(ii(tmpX, tmpY));
		ok[tmpX][tmpY] = true;
	}

	for (int v : adj[u]) {
		if (vis[v]) continue;
		//vis[v] = true;
		DFS(v);
	}
}

void sol() {
	Build_Graph();

	int res = 0;
	for (int i = 1; i <= numVer; ++i) {
		if (vis[i]) continue;
		DFS(i);

		res = max(res, (int) vec.size());
		for (ii u : vec) ok[u.first][u.second] = false;
		vec.clear();
	}
	cout << res << '\n';
}

int main() {
	freopen("input.txt", "r", stdin);

	Read(n);
	for (int i = 1; i <= n; ++i) for (int j = 1; j <= n; ++j) Read(a[i][j]);

	sol();

	return 0;
}