# import pypyjit
# pypyjit.set_param('max_unroll_recursion=-1')
from collections import *
from itertools import *
from functools import *
import math,sys
input = sys.stdin.readline

N,M = map(int,input().split())
A = [list(map(int,input().split())) for _ in range(N)]
if N==1:
    print(0)
    exit()
INF = (1<<60)
dp = [[INF]*M for _ in range(N)]
for i in range(M):
    dp[0][i] = A[0][i]

def segfunc(x, y):
    return min(x,y)

ide_ele = float('inf')


class SegTree:
    """
    Segment Tree
    """

    def __init__(self, init_val, segfunc, ide_ele):
        """
        初期化

        init_val: 配列の初期値
        """
        n = len(init_val)
        self.segfunc = segfunc
        self.ide_ele = ide_ele
        self.num = 1 << (n - 1).bit_length()
        self.tree = [ide_ele] * 2 * self.num
        # 配列の値を葉にセット
        for i in range(n):
            self.tree[self.num + i] = init_val[i]
        # 構築していく
        for i in range(self.num - 1, 0, -1):
            self.tree[i] = segfunc(self.tree[2 * i], self.tree[2 * i + 1])

    def update(self, k, x):
        """
        k番目の値をxに更新

        k: index(0-index)
        x: update value
        """
        k += self.num
        self.tree[k] = x
        while k > 1:
            self.tree[k >> 1] = self.segfunc(self.tree[k], self.tree[k ^ 1])
            k >>= 1

    def query(self, l, r):
        """
        [l, r)のsegfuncしたものを得る

        l: index(0-index)
        r: index(0-index)
        """
        res = self.ide_ele

        l += self.num
        r += self.num
        while l < r:
            if l & 1:
                res = self.segfunc(res, self.tree[l])
                l += 1
            if r & 1:
                res = self.segfunc(res, self.tree[r - 1])
            l >>= 1
            r >>= 1
        return res

for i in range(N-1):
    
    T = SegTree(dp[i],segfunc,ide_ele)
    
    for j in range(M):
        
        dp[i+1][j] = min(dp[i][j] + A[i+1][j],min(T.query(0,j),T.query(j+1,M)) + A[i+1][j]+A[i][j] )
        
print(min(dp[-1]))