n,m=list(map(int,input().split()))
a=[]
for _ in range(n):
    a.append(list(map(int,input().split())))
dp=[[0]*(m) for _ in range(n)]
mi=[0]*(n)
for i in range(n-1):
    for j in range(m):
        if dp[i][j]==mi[i] and i!=0:
            dp[i+1][j]=dp[i][j]+a[i+1][j]
        else:
            dp[i+1][j]=min(mi[i]+a[i+1][j]+a[i][j],dp[i][j]+a[i+1][j])
    mi[i+1]=min(dp[i+1])
print(mi[-1])