fin = open("turtle.in")
fout = open("turtle.out", "w")
h, w = map(int, fin.readline().split(" "))
b = [[0] * w for i in range(h)]
a = [[0] * w for i in range(h)]
for i in range(h):
    c = fin.readline().split()
    for j in range(w):
        a[i][j] = int(c[j])
b[h-1][0] = a[h-1][0]
for i in range(1, w):
    b[h-1][i] = b[h-1][i-1] + a[h-1][i]
for i in range(1, h):
    b[h-i-1][0] = b[h-i][0] + a[h-i-1][0]
for i in range(1, h):
    for j in range(1, w):
        b[h-i-1][j] = max(b[h-i][j], b[h-i-1][j-1]) + a[h-i-1][j]
print(b[0][w-1], file=fout)
fout.close()