n, m = map(int, input().split())
a = []
for i in range(n):
a.append(list(map(int, input().split())))
dp = [[0] * m for i in range(n)]
dp[0][m-1]=a[0][m-1]
for i in range(m-2,-1,-1):
dp[0][i]=a[0][i]+dp[0][i+1]
for j in range(1,n):
dp[j][m-1]=a[j][m-1]+dp[j-1][m-1]
for i in range(1,n):
for j in range(m-2,-1,-1):
dp[i][j]=a[i][j]+max(dp[i-1][j],dp[i][j-1])
print(dp[n-1][0])