#include <bits/stdc++.h>
using namespace std;
#define int long long
#define form2(i, a, b) for (int i = (a); i < (b); ++i)
#define ford2(i, a, b) for (int i = (a-1); i >= b; --i)
#define form(i, n) form2(i, 0, n)
#define ford(i, n) ford2(i, n, 0)
#define chmax(x, v) x = max(x, (v))
#define chmin(x, v) x = min(x, (v))
#define fi first
#define se second
const long long BIG = 1000000000000000000LL;
typedef long long ll;
typedef long double ld;
void cpr(string s, vector<int> v)
{ int i = 0; for (char c : s) { if (c == '$') cout << v[i++]; else cout << c; } cout << '\n'; }
void cpr(string s) { cpr(s, {}); }
void solve();
signed main()
{
ios::sync_with_stdio(false);
cin.tie(0);
solve();
return 0;
}
const int borne = 1005;
int nbLig, nbCol;
int grille[borne][borne];
int dp[borne][borne][5];
// gauche, haut, droite, bas
int dlt[4][2] {{0, -1}, {-1, 0}, {0, 1}, {1, 0}};
int gdp(int lig, int col, int dir);
int calc(int lig, int col, int dir, int dd)
{
int nl = lig+dlt[dd][0], nc = col+dlt[dd][1];
if (nl < 0 || nc < 0 || nl >= nbLig || nc >= nbCol) return BIG;
return gdp(nl, nc, dir)+1;
}
int gdp(int lig, int col, int dir)
{
int &rep = dp[lig][col][dir];
if (rep != -1) return rep;
rep = grille[lig][col]+1;
chmin(rep, calc(lig, col, dir, dir));
chmin(rep, calc(lig, col, dir, (dir+1)%4));
chmin(dp[lig][col][4], rep);
return rep;
}
void solve()
{
fill_n(&dp[0][0][0],borne*borne*5, -1);
form(i, borne) form(j, borne) dp[i][j][4] = BIG;
cin >> nbLig >> nbCol;
form(i, nbLig) form(j, nbCol) cin >> grille[i][j];
form(i, nbLig) form(j, nbCol) gdp(i, j, 0);
form(i, nbLig) ford(j, nbCol) gdp(i, j, 1);
ford(i, nbLig) ford(j, nbCol) gdp(i, j, 2);
ford(i, nbLig) form(j, nbCol) gdp(i, j, 3);
int rep = -BIG;
form(lig, nbLig) form(col, nbCol) {
chmax(rep, grille[lig][col] - dp[lig][col][4]);
}
cout << rep << "\n";
}
