def sumMatrix(matrix, n, m):
    sum = 0
    for i in range(n):
        for o in range(m):
            sum += matrix[i][o]
    return sum

def toInt(x):
    return int(x)

n, m = list(map(toInt, input().split()))
matrix = []
for i in range(n):
    matrix.append(list(map(toInt, input().split())))
sum = sumMatrix(matrix, n, m)
if n % 2 == 1:
    print(sum)
else:
    min = matrix[0][1]
    for i in range(n):
        for o in range(m):
            if i == o:
                continue
            if matrix[i][o] < min:
                min = matrix[i][o]

    sum -= min
    print(sum)