import sys
readline = sys.stdin.readline
N,M = map(int,readline().split())
if N == 1:
    print(0)
    exit(0)
A = [list(map(int,readline().split())) for i in range(N)]
INF = 1 << 60

dp = [INF] * M # 現在i番目が壊されている状態のときの最小コスト
best = INF # その階にいるときの最小コスト
for j in range(M):
    dp[j] = A[0][j]
    if best > dp[j]:
        best = dp[j]
        
for i in range(1, N):
    new_dp = [INF] * M
    next_best = INF
    for j in range(M):
        new_dp[j] = min(dp[j] + A[i][j], best + A[i - 1][j] + A[i][j])
#        print("j",j,"で上がるときのコスト",new_dp[j])
        if next_best > new_dp[j]:
            next_best = new_dp[j]
    dp = new_dp
    best = next_best
#    print("i",i,"dp",dp)
    
print(min(dp))