n, m = map(int, input().split())
prices = [list(map(int, input().split())) for i in range(n)]
max_prices = [[None] * m for i in  range(n)]
max_prices[0][0] = prices[0][0]
for i in range(1, m):
    max_prices[0][i] = max_prices[0][i - 1] + prices[0][i]
for i in range(1, n):
    max_prices[i][0] = max_prices[i - 1][0] + prices[i][0]
for i in range(1, n):
    for j in range(1, m):
        max_prices[i][j] = (max(max_prices[i - 1][j], max_prices[i][j - 1])
                            + prices[i][j])
print(max_prices[n - 1][m - 1])