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

dp = [[10**19]*M for _ in range(N+1)]

for i, a in enumerate(A[0]):
    dp[1][i] = a

minimum = min(dp[1])

for n in range(1,N):
    mini = min(dp[n])
    for m in range(M):
        if dp[n][m] == mini:
            dp[n+1][m] = mini + A[n][m]
        else:
            dp[n+1][m] = min(dp[n][m]+A[n][m], mini+A[n-1][m]+A[n][m])

if N == 1:
    print(0)
else:
    print(min(dp[N]))