N, M = map(int, input().split())
matrix = [list(map(int, input().split())) for _ in range(N)]
sum1 = sum2 = sum3 = sum4 = 0
# 1 가로로 긴 모양
for i in range(N):
for j in range(M - 3):
ssum1 = 0
for k in range(4):
ssum1 += matrix[i][j + k]
if sum1 < ssum1:
sum1 = ssum1
for j in range(M):
for i in range(N - 3):
ssum1 = 0
for k in range(4):
ssum1 += matrix[i + k][j]
if sum1 < ssum1:
sum1 = ssum1
# 2 2*2 정사각형
for i in range(N - 1):
for j in range(N - 1):
ssum2 = 0
for a in range(2):
for b in range(2):
ssum2 += matrix[i + a][j + b]
if sum2 < ssum2:
sum2 = ssum2
#
# 3 2*3
mi1, mj1 = 1, 2
for i in range(N - 1):
for j in range(M - 2):
ssum3 = 0
for a in range(2):
for b in range(3):
ssum3 += matrix[i + a][j + b]
if sum3 < ssum3:
sum3 = ssum3
mi1, mj1 = i, j # 최대합이 되게 하는 시작 인덱스
two_sum1 = [50000]
for a in range(2):
for b in range(2):
two_sum1.append(matrix[mi1 + a][mj1 + b] + matrix[mi1 + a][mj1 + b + 1]) # ㄴ 표시
two_sum1.append(matrix[mi1 + a][mj1 + b - 1] + matrix[mi1 + a][mj1 + b + 1]) # ㅗ 표시
two_sum1.append(matrix[mi1][mj1] + matrix[mi1 + 1][mj1 + 2])
two_sum1.append(matrix[mi1][mj1 + 2] + matrix[mi1 + 1][mj1])
sum3 = sum3 - min(two_sum1)
# 4 3*2
mi2, mj2 = 0, 0
for i in range(N - 2):
for j in range(M - 1):
ssum4 = 0
for a in range(3):
for b in range(2):
ssum4 += matrix[i + a][j + b]
if sum4 < ssum4:
sum4 = ssum4
mi2, mj2 = i, j
two_sum2 = [50000]
for a in range(2):
for b in range(2):
two_sum2.append(matrix[mi2 + a][mj2 + b] + matrix[mi2 + a + 1][mj2 + b]) # ㄴ 표시
two_sum2.append(matrix[mi2][mj2 + a] + matrix[mi2 + b + 1][mj2 + a]) # ㅗ 표시
two_sum2.append(matrix[mi2][mj2] + matrix[mi2 + 2][mj2 + 1])
two_sum2.append(matrix[mi2][mj2 + 1] + matrix[mi2 + 2][mj2])
sum4 = sum4 - min(two_sum2)
print(max(sum1, sum2, sum3, sum4))
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