r,c = [int(i) for i in input().split()]

mat = [[0 for _ in range(c)] for _ in range(r)]

for row in range(r):
    mat[row] = [int(i) for i in input().split()]

suma = sum([sum(row) for row in mat])

if r%2 != 0 or c%2 != 0:
    print(suma)
else:
    min_val = 2000
    for row in range(r):
        for col in range(c):
            if row+col % 2 == 1:
                min_val = min(min_val,mat[row][col])

    print(suma-min_val)