fmin = lambda x, y: x if x < y else y
fmax = lambda x, y: x if x > y else y
def solve(testcase):
n, m = MI()
A = [0 for _ in range(m)]
for i in range(n):
B = LII()
for j in range(m):
if i > 0 and j > 0:
B[j] += fmin(A[j], B[j - 1])
elif i > 0:
B[j] += A[j]
elif j > 0:
B[j] += B[j - 1]
A = B
print(A[m - 1])
for testcase in range(1):
solve(testcase)

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