#include<bits/stdc++.h>
using namespace std;
using uint = unsigned int;
using ll = long long;
using ull = unsigned long long;
template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;
template<class T> using VVV = V<VV<T>>;
template<class T> using VVVV = VV<VV<T>>;
#define rep(i,n) for(ll i=0ll;i<n;i++)
#define REP(i,a,n) for(ll i=a;i<n;i++)
const long long INF = (1LL << 60);
const long long mod99 = 998244353;
const long long mod107 = 1000000007;
const long long mod = mod99;
#define eb emplace_back
#define pb eb
#define be(v) (v).begin(),(v).end()
#define all(i,v) for(auto& i : v)
#define all2(i,j,v) for(auto& [i,j] : v)
#define UQ(v) sort(be(v)), v.erase(unique(be(v)), v.end())
#define LB(x,v) (lower_bound(be(v),(x))-(v).begin())
#define UB(x,v) (upper_bound(be(v),(x))-(v).begin())

template<class T, class U> bool chmin(T& t, const U& u) { if (t > u){ t = u; return 1;} return 0; }
template<class T, class U> bool chmax(T& t, const U& u) { if (t < u){ t = u; return 1;} return 0; }


// cin.tie(nullptr);
// ios::sync_with_stdio(false);
// cout << fixed << setprecision(20);

void solve(){
  ll h,w;
  cin >> h >> w;
  VV<ll> v(h+2, V<ll>(w+2, INF));
  rep(i,h) rep(j,w) cin >> v[i+1][j+1];
  V<tuple<ll,ll,ll>> ww;
  rep(i,h) rep(j,w) ww.eb(v[i+1][j+1], i+1, j+1);
  sort(be(ww));
  VV<ll> ans(h+2, V<ll>(w+2, 0));
  V<ll> dx={0,-1,0,1}, dy={1,0,-1,0};
  for(auto[d,x,y]:ww) rep(i,4){
    ll nx = x+dx[i];
    ll ny = y+dy[i];
    if(d > v[nx][ny]) chmax(ans[x][y], ans[nx][ny]+1);
  }
  ll a = 0;
  all(vv, ans) all(va, vv) chmax(a, va);
  cout << a << endl;
}





int main(){
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int t=1;
  // cin >> t;
  rep(i,t) solve();
}