11048.py

n, m = map(int, input().split())
dp = [list(map(int, input().split())) for _ in range(n)]
for i in range(1, m):
  dp[0][i] += dp[0][i-1]
for i in range(1, n):
  dp[i][0] += dp[i-1][0]

for i in range(1, n):
  for j in range(1, m):
    dp[i][j] += max(dp[i-1][j], dp[i][j-1], dp[i-1][j-1])

print(dp[n-1][m-1])