INF = 1 << 60
N, M = map(int, input().split())
A = []
for _ in range(N):
    A.append(list(map(int, input().split())))

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

dp = [[INF] * M for _ in range(N+1)]
for i in range(M):
    dp[0][i] = A[0][i]

for i in range(N-1):
    mi = min(dp[i])
    for j in range(M):
        # 乗り換えない
        dp[i+1][j] = min(dp[i+1][j], dp[i][j] + A[i+1][j])
        # 乗り換える
        dp[i+1][j] = min(dp[i+1][j], mi + A[i][j] + A[i+1][j])

ans = min(dp[N-1])
print(ans)