#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
ll grid[1001][1001], val[1001][1001][4], mn[1002][1002][4];
int main() {
cin.tie(0)->sync_with_stdio(0);
int n, m;
cin >> n >> m;
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++) {
cin >> grid[i][j];
val[i][j][0] = grid[i][j] - i - j + 1;
val[i][j][1] = grid[i][j] - m + j - i;
val[i][j][2] = grid[i][j] + i + j - 1;
val[i][j][3] = grid[i][j] + m - j + i;
}
ll ans = 0;
memset(mn, 0x3f, sizeof mn);
for (int i = 1; i <= n; i++)
for (int j = 1; j <= m; j++) {
mn[i][j][0] = min({val[i][j][0], mn[i - 1][j][0], mn[i][j - 1][0]});
ans = max(ans, val[i][j][0] - mn[i][j][0]);
}
for (int i = 1; i <= n; i++)
for (int j = m; j; j--) {
mn[i][j][1] = min({val[i][j][1], mn[i - 1][j][1], mn[i][j + 1][1]});
ans = max(ans, val[i][j][1] - mn[i][j][1]);
}
for (int i = n; i; i--)
for (int j = m; j; j--) {
mn[i][j][2] = min({val[i][j][2], mn[i + 1][j][2], mn[i][j + 1][2]});
ans = max(ans, val[i][j][2] - mn[i][j][2]);
}
for (int i = n; i; i--)
for (int j = 1; j <= m; j++) {
mn[i][j][3] = min({val[i][j][3], mn[i + 1][j][3], mn[i][j - 1][3]});
ans = max(ans, val[i][j][3] - mn[i][j][3]);
}
cout << ans - 1;
return 0;
}
