n, m = map(int, input().split())
a = [list(map(int, input().split())) for _ in range(n)]
dp = [a[0]]+[[] for _ in range(n-1)]
b = [min(a[0])]+[10**15]*(n-1)
for i in range(n-1):
    for j in range(m):
        dp[i+1].append(min(b[i]+a[i][j]+a[i+1][j], dp[i][j]+a[i+1][j]))
        b[i+1] = min(b[i+1], dp[i+1][j])
print(b[-1] if n > 1 else 0)