boj_14500ver2

N , M = map(int,input().split())
tList = []
for _ in range(N):
    tList.append(list(map(int,input().split())))

dx = [0, 0, -1, 1]
dy = [1, -1, 0, 0]
visited = [[False for _ in range(M)] for _ in range(N)]
max_sum = -1


def dfs(x, y, num, summ):
    global N, M, tList, dx, dy, max_sum
    if num == 4:
        max_sum = max(max_sum, summ)
        return

    for i in range(4):
        nx = x + dx[i]
        ny = y + dy[i]

        if nx < 0 or ny < 0 or nx >= N or ny >= M:
            continue
        if not visited[nx][ny]:
            visited[nx][ny] = True
            dfs(nx, ny, num + 1, summ + tList[nx][ny])
            visited[nx][ny] = False
def solution():
    global N, M, tList, max_sum

    for i in range(N):
        for j in range(M):
            visited[i][j] = True
            dfs(i, j, 1, tList[i][j])
            visited[i][j] = False
            
def pink(tList, a, b, max):
    for i in range(a-2):
        for j in range(b-1):
            sum = tList[i][j]+tList[i+1][j]+tList[i+2][j]+tList[i+1][j+1]
            if sum > max:
                max = sum
            sum = 0
    for i in range(a-1):
        for j in range(b-2):
            sum = tList[i+1][j]+tList[i+1][j+1]+tList[i+1][j+2]+tList[i][j+1]
            if sum > max:
                max = sum
            sum = 0
    for i in range(a-2):
        for j in range(b-1):
            sum = tList[i+1][j]+tList[i][j+1]+tList[i+1][j+1]+tList[i+2][j+1]
            if sum > max:
                max = sum
            sum = 0
    for i in range(a-1):
        for j in range(b-2):
            sum = tList[i][j]+tList[i][j+1]+tList[i][j+2]+tList[i+1][j+1]
            if sum > max:
                max = sum
            sum = 0
    return max

solution()
max_sum = pink(tList,N,M,max_sum)

print(max_sum)





########################################
best
####################################
import sys; input = sys.stdin.readline

def dfs(r, c, idx, total):
    global ans
    if idx == 3:
        ans = max(ans, total)
        return
    else:
        for i in range(4):
            nr = r + dr[i]
            nc = c + dc[i]
            if 0 <= nr < N and 0 <= nc < M and visit[nr][nc] == 0:
                if idx == 1:
                    visit[nr][nc] = 1
                    dfs(r, c, idx + 1, total + arr[nr][nc])
                    visit[nr][nc] = 0
                visit[nr][nc] = 1
                dfs(nr, nc, idx + 1, total + arr[nr][nc])
                visit[nr][nc] = 0


N, M = map(int, input().split())
arr = [list(map(int, input().split())) for _ in range(N)]
visit = [([0] * M) for _ in range(N)]
dr = [-1, 0, 1, 0]
dc = [0, 1, 0, -1]
ans = 0
max_val = max(map(max, arr))

for r in range(N):
    for c in range(M):
        visit[r][c] = 1
        dfs(r, c, 0, arr[r][c])
        visit[r][c] = 0

print(ans)