#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>

int max(int a, int b);
void dfs(int** arr, bool** visited, int x, int y, int n, int m, int currentSum, int* currentMax, int depth);
void T_block_Search(int** arr, int n, int m, int* currentMax);

int main(){
    int N, M;
    scanf("%d %d",&N, &M);
    int** canvas = (int**)malloc(sizeof(int*)*N);
    bool** visited = (bool**)malloc(sizeof(bool*)*N);
    for(int i=0; i<N; i++){
        canvas[i] = (int*)malloc(sizeof(int)*M);
        visited[i] = (bool*)malloc(sizeof(bool)*M);
        for(int j=0; j<M; j++){
            scanf("%d",&canvas[i][j]);
            visited[i][j] = false;
        }
    }

    int maxValue = 0;
    for(int x=0; x<M; x++){
        for(int y=0; y<N; y++){
            visited[y][x] = true;
            dfs(canvas, visited, x, y, N, M, canvas[y][x], &maxValue, 1);
            visited[y][x] = false;
        }
    }
    
    T_block_Search(canvas, N, M, &maxValue);
    
    printf("%d\n",maxValue);
    
    for(int i=0; i<N; i++){
        free(canvas[i]);
        free(visited[i]);
    }
    free(canvas);
    free(visited);

    return 0;
}

int max(int a, int b){
    return (a>b) ? a : b;
}

void dfs(int** arr, bool** visited, int x, int y, int n, int m, int currentSum, int* currentMax, int depth){
    if(depth==4) {
        *currentMax = max(currentSum, *currentMax);
        return;
    }

    int dx[4] = {1,-1,0,0};
    int dy[4] = {0,0,1,-1};

    for(int i=0; i<4; i++){
        int nx = x + dx[i];
        int ny = y + dy[i];
        
        if(nx<0 || ny<0 || nx>=m || ny>=n || visited[ny][nx]) continue;

        visited[ny][nx] = true;
        dfs(arr, visited, nx, ny, n, m, currentSum + arr[ny][nx], currentMax, depth + 1);
        visited[ny][nx] = false;
    }
}

void T_block_Search(int** arr, int n, int m, int* currentMax){
    for(int y=0; y<n; y++){
        for(int x=0; x<m; x++){
            //ㅏ
            if(x+1<m && y>=1 && y+1<n) *currentMax = max(*currentMax, arr[y][x]+arr[y][x+1]+arr[y-1][x]+arr[y+1][x]);
            //ㅜ
            if(x>=1 && x+1<m && y+1<n) *currentMax = max(*currentMax, arr[y][x]+arr[y][x+1]+arr[y][x-1]+arr[y+1][x]);
            //ㅓ
            if(x>=1 && y>=1 && y+1<n) *currentMax = max(*currentMax, arr[y][x]+arr[y][x-1]+arr[y-1][x]+arr[y+1][x]);
            //ㅗ
            if(x>=1 && x+1<m && y>=1) *currentMax = max(*currentMax, arr[y][x]+arr[y][x+1]+arr[y][x-1]+arr[y-1][x]);
        }
    }
}