n,m = map(int,input().split())
a = [list(map(int,input().split())) for _ in range(n)]
dp = [0] * (m)
import sys
if n == 1:
    sys.exit(print(0))
if m == 1:
    sys.exit(print(sum(e[0] for e in a)))
for i in range(m):
    dp[i] = a[0][i] + a[1][i]
# print(dp)
for i in range(2,n):
    mins = []
    n_dp = [0] * (m)
    for j in range(m):
        mins.append(dp[j])
    mins.sort()
    for j in range(m):
        if dp[j] == mins[0]:
            n_dp[j] = min(a[i][j] + a[i-1][j] + mins[1],a[i][j] + dp[j])
        else:
            n_dp[j] =  min(a[i][j] + a[i-1][j] + mins[0],a[i][j] + dp[j])
    dp = n_dp
#     print(dp,mins)
print(min(dp))