import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }

string COLOR(string s = "") { return "\x1b[" ~ s ~ "m"; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum DX = [+1, 0, -1, 0];
enum DY = [0, +1, 0, -1];

void main() {
  try {
    for (; ; ) {
      const M = readInt;
      const N = readInt;
      auto A = new int[][](M + 2, N + 2);
      foreach (x; 1 .. M + 1) foreach (y; 1 .. N + 1) {
        A[x][y] = readInt + 1;
      }
      
      alias Entry = Tuple!(int, "a", int, "x", int, "y");
      Entry[] es;
      foreach (x; 1 .. M + 1) foreach (y; 1 .. N + 1) {
        es ~= Entry(A[x][y], x, y);
      }
      es.sort;
      
      auto dp = new int[][](M + 2, N + 2);
      foreach (e; es) {
        const x = e.x, y = e.y;
        static foreach (dir; 0 .. 4) {
          if (A[x][y] > A[x + DX[dir]][y + DY[dir]]) {
            chmax(dp[x][y], dp[x + DX[dir]][y + DY[dir]] + 1);
          }
        }
      }
      debug {
        foreach (x; 0 .. M + 2) writeln(dp[x]);
      }
      
      int ans;
      foreach (x; 1 .. M + 1) foreach (y; 1 .. N + 1) {
        chmax(ans, dp[x][y]);
      }
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}