using System;
using System.Linq;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using StringBuilder = System.Text.StringBuilder;
using System.Numerics;
using Number = System.Int64;
namespace Program
{
public class Solver
{
public void Solve()
{
var h = sc.Integer();
var w = sc.Integer();
var map = Enumerate(h, x => sc.Long(w));
var map2 = Enumerate(w, x => new long[h]);
for (int i = 0; i < h; i++)
for (int j = 0; j < w; j++)
map2[j][i] = map[i][j];
foreach(var x in map2)
Debug.WriteLine(x.AsJoinedString());
var u = solve(map, h, w);
var v = solve(map2, w, h);
IO.Printer.Out.WriteLine(Math.Max(u, v));
}
public long solve(long[][] map, int h, int w)
{
var cum = createCumulativeSum(map);
var maU = new long[h];
var maL = new long[h];
for (int i = 0; i < h; i++)
maU[i] = maL[i] = -1L << 60;
for (int i = 0; i < h; i++)
{
for (int j = i; j < h; j++)
{
var val = new long[w];
for (int k = 0; k < w; k++)
val[k] = getArea(cum, i, k, j + 1, k + 1);
var max = -1L << 60;
for (int k = 0; k < w; k++)
max = Math.Max(max, val[k]);
long v = 0;
for (int k = 0; k < w;)
{
while (k < w && val[k] + v >= 0)
{
v += val[k];
max = Math.Max(max, v);
k++;
}
if (k < w && val[k] + v < 0)
{
v = 0;
k++;
}
}
maU[i] = Math.Max(maU[i], max);
maL[j] = Math.Max(maL[j], max);
}
}
for (int i = h - 1; i > 0; i--)
{
maU[i - 1] = Math.Max(maU[i - 1], maU[i]);
}
for (int i = 0; i < h - 1; i++)
{
maL[i + 1] = Math.Max(maL[i + 1], maL[i]);
}
var ans = -1L << 60;
for (int i = 1; i < h; i++)
{
ans = Math.Max(ans, maU[i] + maL[i - 1]);
}
return ans;
}
#region 累積和
static public Func<long[][], long[][]> createCumulativeSum = s =>
{
int n = s.Length, m = s[0].Length;
var a = new long[n + 1][];
for (int i = 0; i <= n; i++)
a[i] = new long[m + 1];
for (int i = 0; i < n; i++)
for (int j = 0; j < m; j++)
a[i + 1][j + 1] = a[i + 1][j] + a[i][j + 1] - a[i][j] + s[i][j];
return a;
};
/// <summary>元のテーブルにおける[x1,x2),[y1,y2)の矩形領域に含まれる値の和を取ってくる</summary>
static public Func<long[][], int, int, int, int, long> getArea = (a, x1, y1, x2, y2) =>
{
if (x1 >= x2 || y1 >= y2) throw new ArgumentException("x1<x2 && y1<y2");
return a[x2][y2] - a[x1][y2] - a[x2][y1] + a[x1][y1];
};
#endregion
public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());
static T[] Enumerate<T>(int n, Func<int, T> f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; }
static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
}
}
#region main
static class Ex
{
static public string AsString(this IEnumerable<char> ie) { return new string(System.Linq.Enumerable.ToArray(ie)); }
static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
static public void Main()
{
var solver = new Program.Solver();
solver.Solve();
Program.IO.Printer.Out.Flush();
}
}
#endregion
#region Ex
namespace Program.IO
{
using System.IO;
using System.Text;
using System.Globalization;
public class Printer : StreamWriter
{
static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
public static Printer Out { get; set; }
public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
}
public class StreamScanner
{
public StreamScanner(Stream stream) { str = stream; }
public readonly Stream str;
private readonly byte[] buf = new byte[1024];
private int len, ptr;
public bool isEof = false;
public bool IsEndOfStream { get { return isEof; } }
private byte read()
{
if (isEof) return 0;
if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } }
return buf[ptr++];
}
public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; }
public string Scan()
{
var sb = new StringBuilder();
for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
sb.Append(b);
return sb.ToString();
}
public string ScanLine()
{
var sb = new StringBuilder();
for (var b = Char(); b != '\n'; b = (char)read())
if (b == 0) break;
else if (b != '\r') sb.Append(b);
return sb.ToString();
}
public long Long()
{
if (isEof) return long.MinValue;
long ret = 0; byte b = 0; var ng = false;
do b = read();
while (b != 0 && b != '-' && (b < '0' || '9' < b));
if (b == 0) return long.MinValue;
if (b == '-') { ng = true; b = read(); }
for (; true; b = read())
{
if (b < '0' || '9' < b)
return ng ? -ret : ret;
else ret = ret * 10 + b - '0';
}
}
public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; }
private T[] enumerate<T>(int n, Func<T> f)
{
var a = new T[n];
for (int i = 0; i < n; ++i) a[i] = f();
return a;
}
public char[] Char(int n) { return enumerate(n, Char); }
public string[] Scan(int n) { return enumerate(n, Scan); }
public double[] Double(int n) { return enumerate(n, Double); }
public int[] Integer(int n) { return enumerate(n, Integer); }
public long[] Long(int n) { return enumerate(n, Long); }
}
}
#endregion