from heapq import heappop, heappush


INF = float('inf')
N, M = map(int, input().split())
A = [list(map(int, input().split())) for _ in range(N)]
edges = [[] for _ in range(2 * N * M)]
for i in range(N):
    for j in range(M):
        edges[N * M + i].append((i * M + j, A[i][j]))
        edges[i * M + j].append((N * M + i, 0))
for i in range(N - 1):
    for j in range(M):
        edges[i * M + j].append(((i + 1) * M + j, A[i + 1][j]))


S = N * M
dist = [INF] * (N * (M + 1))
dist[S] = 0
hq = [(0, S)]
done = [False] * (N * (M + 1))
while hq:
    _, now = heappop(hq)
    if done[now]:
        continue
    done[now] = True
    for nxt, cost in edges[now]:
        if dist[nxt] > dist[now] + cost:
            dist[nxt] = dist[now] + cost
            heappush(hq, (dist[nxt], nxt))

print(dist[-1])