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

struct cell {
    int x, y;
};

const int dx[4] = {1, -1, 0, 0};
const int dy[4] = {0, 0, 1, -1};

int main() {
    int H, W;
    cin >> H >> W;
    vector A(H, vector(W, 0));
    for(int i = 0; i < H; i++) {
        for(int j = 0; j < W; j++) {
            cin >> A[i][j];
        }
    }
    auto compare = [&](cell a, cell b) {
        return !(A[a.x][a.y] < A[b.x][b.y]);
    };
    priority_queue<cell, vector<cell>, decltype(compare)> pq{compare};
    for(int i = 0; i < H; i++) for(int j = 0; j < W; j++) pq.push({i, j});
    vector dp(H, vector(W, 1));
    while(!pq.empty()) {
        cell C = pq.top(); pq.pop();
        for(int dir = 0; dir < 4; dir++) {
            int nx(C.x+dx[dir]), ny(C.y+dy[dir]);
            if(0 <= nx && nx < H && 0 <= ny && ny < W) {
                if(A[C.x][C.y] < A[nx][ny]) dp[nx][ny] = max(dp[C.x][C.y]+1, dp[nx][ny]);
            }
        }
    }
    int ans(0);
    for(int i = 0; i < H; i++) {
        for(int j = 0; j < W; j++) {
            ans = max(dp[i][j], ans);
        }
    }
    cout << ans << endl;
    return 0;
}