n,m = map(int,input().split())
A = [list(map(int,input().split())) for i in range(n)]

if n == 1:
    print(0)
    exit()
dp = A[0]

for i in range(1,n):
    ndp = [0]*m
    mi = min(dp)
    for j in range(m):
        ndp[j] = dp[j]+A[i][j]
        ndp[j] = min(ndp[j],mi+A[i][j]+A[i-1][j])
    dp = ndp
print(min(dp))