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


import sys
if N == 1:
    print(0)
    exit()
inf = 10 ** 15
dp = [[inf] * M for _ in range(N)]

for i in range(M):
    dp[0][i] = A[0][i]
for i in range(1,N):
    s = min(dp[i-1])
    for j in range(M):
        dp[i][j] = min(dp[i-1][j] + A[i][j],s + A[i][j] + A[i-1][j])
ans = inf
for j in range(M):
    if dp[-1][j] < ans:
        ans = dp[-1][j]
print(ans)