INF = 10**18
N, M = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(N)]

if N == 1:
    exit(print(0))

DP = [[INF] * (M) for _ in range(N)]

# i == 0
for j in range(M):
    DP[0][j] = 0

# i == 1
for j in range(M):
    DP[1][j] = A[0][j] + A[1][j]

premin = min(DP[1])

if N == 2:
    exit(print(premin))

# もらうDP
for i in range(2, N):
    for j in range(M):
        DP[i][j] = min(
            DP[i - 1][j] + A[i][j],
            premin + A[i - 1][j] + A[i][j]
        )
    premin = min(DP[i])

ans = min(DP[-1])
print(ans)