from collections import deque


class Dinic:
    def __init__(self, N):
        self.N = N
        self.G = [[] for i in range(N)]

    def add_edge(self, fr, to, cap):
        forward = [to, cap, None]
        forward[2] = backward = [fr, 0, forward]
        self.G[fr].append(forward)
        self.G[to].append(backward)

    def add_multi_edge(self, v1, v2, cap1, cap2):
        edge1 = [v2, cap1, None]
        edge1[2] = edge2 = [v1, cap2, edge1]
        self.G[v1].append(edge1)
        self.G[v2].append(edge2)

    def bfs(self, s, t):
        self.level = level = [None]*self.N
        deq = deque([s])
        level[s] = 0
        G = self.G
        while deq:
            v = deq.popleft()
            lv = level[v] + 1
            for w, cap, _ in G[v]:
                if cap and level[w] is None:
                    level[w] = lv
                    deq.append(w)
        return level[t] is not None

    def dfs(self, v, t, f):
        if v == t:
            return f
        level = self.level
        for e in self.it[v]:
            w, cap, rev = e
            if cap and level[v] < level[w]:
                d = self.dfs(w, t, min(f, cap))
                if d:
                    e[1] -= d
                    rev[1] += d
                    return d
        return 0

    def flow(self, s, t):
        flow = 0
        INF = 10**9 + 7
        G = self.G
        while self.bfs(s, t):
            *self.it, = map(iter, self.G)
            f = INF
            while f:
                f = self.dfs(s, t, INF)
                flow += f
        return flow


h, w = map(int, input().split())
assert (3 <= min(h, w) <= max(h, w) <= 800)
h -= 2
a = [list(map(int, input().split())) for _ in range(h)]
def ij(i, j, t): return (i*w+j)*2+t


dinic = Dinic(h*w*2+2)
inf = 10**10
s = h*w*2
for i in range(h):
    for j in range(w):
        if a[i][j] != -1:
            dinic.add_edge(ij(i, j, 0), ij(i, j, 1), a[i][j])
        else:
            dinic.add_edge(ij(i, j, 0), ij(i, j, 1), inf)
        if i != h-1:
            dinic.add_edge(ij(i, j, 1), ij(i+1, j, 0), inf)
            dinic.add_edge(ij(i+1, j, 1), ij(i, j, 0), inf)
        if j != w-1:
            dinic.add_edge(ij(i, j, 1), ij(i, j+1, 0), inf)
            dinic.add_edge(ij(i, j+1, 1), ij(i, j, 0), inf)
for j in range(w):
    dinic.add_edge(s, ij(0, j, 0), inf)
    dinic.add_edge(ij(h-1, j, 1), s+1, inf)
ans = dinic.flow(s, s+1)
if ans >= inf:
    print(-1)
else:
    print(ans)