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

    if N==1:
        return 0

    inf=float("inf")
    DP=[[inf]*M for _ in range(N)]
    T=[inf]*N; T[0]=0

    for i in range(N-1):
        Ai=A[i]; Aii=A[i+1]
        DPi=DP[i]; DPii=DP[i+1]
        for j in range(M):
            DPii[j]=min(DPi[j]+Aii[j], T[i]+Ai[j]+Aii[j])
        T[i+1]=min(DP[i+1])

    return T[N-1]

#==================================================
print(solve())