/* -*- coding: utf-8 -*-
 *
 * 2639.cc:  No.2639 Longest Increasing Walk - yukicoder
 */

#include<cstdio>
#include<vector>
#include<queue>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_H = 500;
const int MAX_W = 500;
const int MAX_N = MAX_H * MAX_W;

/* typedef */

typedef vector<int> vi;
typedef queue<int> qi;

/* global variables */

int as[MAX_N], pns[MAX_N], ds[MAX_N];
vi nbrs[MAX_N];

/* subroutines */

/* main */

int main() {
  int h, w;
  scanf("%d%d", &h, &w);
  int n = h * w;
  for (int i = 0; i < n; i++) scanf("%d", as + i);

  for (int i = 0, u = 0; i < h; i++)
    for (int j = 0; j < w; j++, u++) {
      if (i + 1 < h) {
	int v = u + w;
	if (as[u] < as[v]) nbrs[u].push_back(v), pns[v]++;
	else if (as[u] > as[v]) nbrs[v].push_back(u), pns[u]++;
      }
      if (j + 1 < w) {
	int v = u + 1;
	if (as[u] < as[v]) nbrs[u].push_back(v), pns[v]++;
	else if (as[u] > as[v]) nbrs[v].push_back(u), pns[u]++;
      }
    }

  qi q;
  for (int u = 0; u < n; u++)
    if (pns[u] == 0) q.push(u), ds[u] = 1;

  int maxd = 0;
  while (! q.empty()) {
    int u = q.front(); q.pop();
    maxd = max(maxd, ds[u]);
    
    for (auto v: nbrs[u]) {
      ds[v] = max(ds[v], ds[u] + 1);
      if (--pns[v] == 0) q.push(v);
    }
  }

  printf("%d\n", maxd);

  return 0;
}