INF = 1<<60


N,M = map(int,input().split())
A = [list(map(int,input().split())) for _ in range(N)]
if N == 1:
    print(0)
    exit()

dp = [[INF] * M for _ in range(N)]
val = INF
for j in range(M):
    dp[1][j] = A[0][j] + A[1][j]
    val = min(val , dp[1][j])

for i in range(2,N):
    nxt_val = INF
    for j in range(M):
        dp[i][j] = min(dp[i-1][j] + A[i][j] , val + A[i-1][j] + A[i][j] )
        nxt_val = min(nxt_val,dp[i][j])
    val = nxt_val

print(min(dp[N-1][:]))