#include <bits/stdc++.h>
using namespace std;
const int N_ = 1050, M_ = 1050;
int N, M, A[N_][M_];
int ans = -int(1e9);
void go() {
vector< vector<int> > mn(N+1, vector<int>(M+1, int(1e9)+1));
vector< vector<int> > mx(N+1, vector<int>(M+1, -1));
for(int i = 1; i <= N; i++) {
for(int j = 1; j <= M; j++) {
int cur_min = min(mn[i][j-1], mn[i-1][j]);
int cur_max = max(mx[i][j-1], mx[i-1][j]);
ans = max(ans, max(A[i][j] - cur_min, -A[i][j] + cur_max) - (i + j) - 1);
mn[i][j] = min(cur_min, A[i][j] - (i + j));
mx[i][j] = max(cur_max, A[i][j] + (i + j));
}
}
}
int main() {
ios::sync_with_stdio(false);
cin >> N >> M;
for(int i = 1; i <= N; i++) {
for(int j = 1; j <= M; j++) {
cin >> A[i][j];
}
}
// assert(1 <= N * M && N * M <= 20);
go();
for(int i = 1; i <= N; i++) {
reverse(A[i]+1, A[i]+M+1);
}
go();
cout << ans << endl;
return 0;
}
