#![allow(non_snake_case, unused_imports, unused_must_use)]
use std::io::{self, prelude::*};
use std::str;

fn main() {
    let (stdin, stdout) = (io::stdin(), io::stdout());
    let mut scan = Scanner::new(stdin.lock());
    let mut out = io::BufWriter::new(stdout.lock());

    macro_rules! input {
        ($T: ty) => {
            scan.token::<$T>()
        };
        ($T: ty, $N: expr) => {
            (0..$N).map(|_| scan.token::<$T>()).collect::<Vec<_>>()
        };
    }

    let H = input!(usize);
    let W = input!(usize);
    let A = (0..H).map(|_| input!(usize, W)).collect::<Vec<_>>();

    let mut ans = 0;

    // 横
    for i in 0..H + 2 {
        for j in i + 1..H + 2 {
            let mut seen = vec![vec![false; W]; H];

            if i == 0 {
                let mut ny = 0;
                let mut nx = 0;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    ny += 1;
                    nx += 1;
                }
            } else if 0 < i && i < H + 1 {
                let mut ny = i - 1;
                let mut nx = 0;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    nx += 1;
                }
            } else {
                let mut ny = H - 1;
                let mut nx = 0;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    if ny == 0 {
                        break;
                    }

                    ny -= 1;
                    nx += 1;
                }
            }

            if j == 0 {
                let mut ny = 0;
                let mut nx = 0;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    ny += 1;
                    nx += 1;
                }
            } else if 0 < j && j < H + 1 {
                let mut ny = j - 1;
                let mut nx = 0;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    nx += 1;
                }
            } else {
                let mut ny = H - 1;
                let mut nx = 0;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    if ny == 0 {
                        break;
                    }

                    ny -= 1;
                    nx += 1;
                }
            }

            let mut score = 0;

            for i in 0..H {
                for j in 0..W {
                    if seen[i][j] {
                        score += A[i][j];
                    }
                }
            }

            ans = std::cmp::max(ans, score);
        }
    }

    for i in 0..W + 2 {
        for j in i + 1..W + 2 {
            let mut seen = vec![vec![false; W]; H];

            if i == 0 {
                let mut ny = 0;
                let mut nx = 0;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    ny += 1;
                    nx += 1;
                }
            } else if 0 < i && i < W + 1 {
                let mut ny = 0;
                let mut nx = i - 1;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    ny += 1;
                }
            } else {
                let mut ny = 0;
                let mut nx = W - 1;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    if nx == 0 {
                        break;
                    }

                    ny += 1;
                    nx -= 1;
                }
            }

            if j == 0 {
                let mut ny = 0;
                let mut nx = 0;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    ny += 1;
                    nx += 1;
                }
            } else if 0 < j && j < W + 1 {
                let mut ny = 0;
                let mut nx = j - 1;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    ny += 1;
                }
            } else {
                let mut ny = 0;
                let mut nx = W - 1;
                loop {
                    if ny < H && nx < W {
                        seen[ny][nx] = true;
                    } else {
                        break;
                    }

                    if nx == 0 {
                        break;
                    }

                    ny += 1;
                    nx -= 1;
                }
            }

            let mut score = 0;

            for i in 0..H {
                for j in 0..W {
                    if seen[i][j] {
                        score += A[i][j];
                    }
                }
            }

            ans = std::cmp::max(ans, score);
        }
    }

    writeln!(out, "{}", ans);
}

struct Scanner<R> {
    reader: R,
    buf_str: Vec<u8>,
    buf_iter: str::SplitWhitespace<'static>,
}
impl<R: BufRead> Scanner<R> {
    fn new(reader: R) -> Self {
        Self {
            reader,
            buf_str: vec![],
            buf_iter: "".split_whitespace(),
        }
    }
    fn token<T: str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buf_iter.next() {
                return token.parse().ok().expect("Failed parse");
            }
            self.buf_str.clear();
            self.reader
                .read_until(b'\n', &mut self.buf_str)
                .expect("Failed read");
            self.buf_iter = unsafe {
                let slice = str::from_utf8_unchecked(&self.buf_str);
                std::mem::transmute(slice.split_whitespace())
            }
        }
    }
}