#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
istream &operator>>(istream &is, modint &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint &a) { return os << a.val(); }
istream &operator>>(istream &is, modint998244353 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint998244353 &a) { return os << a.val(); }
istream &operator>>(istream &is, modint1000000007 &a) { long long v; is >> v; a = v; return is; }
ostream &operator<<(ostream &os, const modint1000000007 &a) { return os << a.val(); } 

typedef long long ll;
typedef vector<vector<int>> Graph;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define FOR(i,l,r) for (int i = l;i < (int)(r); i++)
#define rep(i,n) for (int i = 0;i < (int)(n); i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define my_sort(x) sort(x.begin(), x.end())
#define my_max(x) *max_element(all(x))
#define my_min(x) *min_element(all(x))
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = (1<<30) - 1;
const ll LINF = (1LL<<62) - 1;
const int MOD = 998244353;
const int MOD2 = 1e9+7;
const double PI = acos(-1);
vector<int> di = {1,0,-1,0};
vector<int> dj = {0,1,0,-1};

#ifdef LOCAL
#  include <debug_print.hpp>
#  define debug(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define debug(...) (static_cast<void>(0))
#endif

vector<int> topological_sort(Graph &g){
    int N = g.size();
    vector<int> deg(N);
    for(int from_=0;from_<N;from_++){
        for(auto nxt_: g[from_]){
            deg[nxt_]++;
        }
    }
    queue<int> que;
    rep(i,N){
        if (deg[i] == 0) que.push(i);
    }
    vector<int> res;
    while(!que.empty()){
        auto now = que.front(); que.pop();
        res.push_back(now);
        for(auto nxt:g[now]){
            deg[nxt]--;
            if (deg[nxt] == 0){
                que.push(nxt);
            }
        }
    }
    return res;
}

int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    int H, W; cin >> H >> W;
    vector A(H, vector<int>(W));
    rep(i,H)rep(j,W) cin >> A[i][j];

    auto id = [&](int i, int j){
        return i * W + j;
    };
    int V = H * W;
    Graph g(V);
    vector<int> deg(V, 0);
    rep(i,H)rep(j,W){
        rep(d,4){
            int ni = i + di[d];
            int nj = j + dj[d];
            if(ni < 0 || ni >= H || nj < 0 || nj >= W)continue;
            if(A[i][j] < A[ni][nj]) {
                deg[id(ni, nj)]++;
                g[id(i, j)].push_back(id(ni, nj));
            }
        }
    }
    vector<int> dp(V, -INF);
    queue<int> que;
    rep(i,V)if(deg[i]==0){
        que.push(i);
        dp[i] = 1;
    }
    while(!que.empty()){
        int now = que.front(); que.pop();
        for(int nxt : g[now]){
            chmax(dp[nxt], dp[now] + 1);
            deg[nxt]--;
            if(deg[nxt]==0)que.push(nxt);
        }
    }


    cout << *max_element(all(dp)) << endl;
}