import sys
# import pypyjit
import itertools
import heapq
import math
import bisect
from collections import deque, defaultdict
from functools import lru_cache, cmp_to_key


# for AtCoder Easy test
if __file__ == 'prog.py':
    pass
else:
    sys.setrecursionlimit(10 ** 6)
# pypyjit.set_param('max_unroll_recursion=-1')

input = sys.stdin.readline


def readints(): return map(int, input().split())
def readlist(): return list(readints())
def readstr(): return input()[:-1]


N, M = readints()
A = [readlist() for _ in range(N)]
if N == 1:
    print(0)
    exit()

INF = 1 << 50
B = [(INF, -1)]
for i in range(N - 1):
    acc = INF
    idx = None
    for j in range(M):
        if A[i][j] + A[i + 1][j] < acc:
            acc = A[i][j] + A[i + 1][j]
            idx = j
    B.append((acc, idx))

dp = [[INF for _ in range(M)] for _ in range(N + 1)]
dp[0] = [0] * M
for i in range(N):
    mc, mi = B[i]
    for j in range(M):
        dp[i + 1][j] = min(dp[i + 1][j], dp[i][j] + A[i][j])
        dp[i + 1][mi] = min(dp[i + 1][mi], dp[i][j] + mc)
print(min(dp[N]))