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

#define REP(i, n) for(ll i = 0;i < n;i++)
#define REPR(i, n) for(ll i = n;i >= 0;i--)
#define FOR(i, m, n) for(ll i = m;i < n;i++)
#define FORR(i, m, n) for(ll i = m;i >= n;i--)
#define REPO(i, n) for(ll i = 1;i <= n;i++)
#define ll long long
#define INF (ll)1ll << 60
#define MINF (-1 * INF)
#define ALL(n) n.begin(),n.end()
#define MOD (ll)1000000007
#define P pair<ll, ll>

#define PP pair<ll, P>
ll h, w, ans, s[510][510], dp[510][510];
ll vx[4] = {1, -1, 0, 0}, vy[4] = {0, 0, -1, 1};
vector<PP> v;
int main(){
    cin >> h >> w;
    REP(i, h){
        REP(j, w){
            cin >> s[i][j];
            v.push_back(PP(s[i][j], P(i, j)));
        }
    }
    sort(ALL(v));
    REP(i, v.size()){
        ll x = v[i].second.first, y = v[i].second.second;
        ans = max(ans, dp[x][y] + 1);
        REP(j, 4){
            ll nx = x + vx[j], ny = y + vy[j];
            if(0 > nx or nx >= h or 0 > ny or ny >= w)continue;
            if(s[nx][ny] > s[x][y]){
                dp[nx][ny] = max(dp[nx][ny], dp[x][y] + 1);
            }
        }
    }
    cout <<ans << endl;
}