import sys
#input = sys.stdin.readline
#input = sys.stdin.buffer.readline #文字列はダメ
#sys.setrecursionlimit(1000000)
import math
import bisect
#import itertools
#import random
from heapq import heapify, heappop, heappush
from collections import defaultdict 
#from collections import deque
import copy #DeepCopy: hoge = [_[:] for _ in hogehoge]
#from functools import lru_cache
#@lru_cache(maxsize=None)
MOD = pow(10,9) + 7
#MOD = 998244353
#dx = [1,0,-1,0]
#dy = [0,1,0,-1]
#dx8 = [1,1,0,-1,-1,-1,0,1]
#dy8 = [0,1,1,1,0,-1,-1,-1]

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

    if N == 1:
        print(0)
        exit()

    dp = A[0]
    mn = min(dp)
    loc = set([])
    for i in range(M):
        if dp[i] == mn:
            loc.add(i)

    for i in range(1,N):
        p = [0]*M
        p,dp = dp,p
        for j in range(M):
            if j in loc:
                dp[j] = mn + A[i][j]
            else:
                dp[j] = min(p[j] + A[i][j], mn + A[i-1][j] + A[i][j])
        
        mn = min(dp)
        loc = set([])
        for j in range(M):
            if dp[j] == mn:
                loc.add(j)
        # print(dp)
        
    print(min(dp))


if __name__ == '__main__':
    main()