N,M = map(int,input().split())
A = [list(map(int,input().split())) for _ in range(N)]
INFTY = 10**13
dp = [[INFTY for _ in range(M)] for _ in range(N)]
dpmin = [INFTY]*N
for j in range(M):
    dp[0][j] = 0
    dpmin[0] = min(dpmin[0],dp[0][j])
if N>=2:
    for j in range(M):
        dp[1][j] = A[0][j]+A[1][j]
        dpmin[1] = min(dpmin[1],dp[1][j])
for i in range(2,N):
    for j in range(M):
        dp[i][j] = dp[i-1][j]+A[i][j]
        if dpmin[i-1]!=dp[i-1][j]:
            dp[i][j] = min(dp[i][j],dpmin[i-1]+A[i-1][j]+A[i][j])
        dpmin[i] = min(dpmin[i],dp[i][j])
print(min(dp[N-1]))