#include <bits/stdc++.h> using namespace std; using ll = long long; using vb = vector<bool>; using vvb = vector<vb>; using vi = vector<int>; using vvi = vector<vi>; using vl = vector<ll>; using vvl = vector<vl>; using vc = vector<char>; using vvc = vector<vc>; using vs = vector<string>; const ll mod = 1e9 + 7,inf = 1e18; #define pb push_back #define fast ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0); void setIO() { fast; } int main() { setIO(); int n,m; cin>>n>>m; vvi a(n + 1,vi(m + 1)),dp(n + 1,vi(m + 1)); for (int i = 1;i<=n;i++)for (int j = 1;j<=m;j++)cin>>a[i][j]; for (int i = 1;i<=n;i++){ for (int j = 1;j<=m;j++){ dp[i][j] = a[i][j] - 1; dp[i][j] = max(dp[i][j],dp[i - 1][j] - 1); dp[i][j] = max(dp[i][j],dp[i][j - 1] - 1); } } for (int i = n;i>=1;i--){ for (int j = m;j>=1;j--){ if (i + 1 <= n)dp[i][j] = max(dp[i][j], dp[i + 1][j] - 1); if (j + 1 <= m)dp[i][j] = max(dp[i][j], dp[i][j + 1] - 1); } } int ans = dp[1][1] - a[1][1]; for (int i = 1;i<=n;i++) for (int j = 1;j<=m;j++) ans = max(ans,dp[i][j] - a[i][j]); cout<<ans; return 0; }