import sys
from collections import deque

class Edge:
    def __init__(self, to, rev, cap):
        self.to = to
        self.rev = rev
        self.cap = cap

class Dinic:
    def __init__(self, n):
        self.size = n
        self.graph = [[] for _ in range(n)]
    
    def add_edge(self, fr, to, cap):
        forward = Edge(to, len(self.graph[to]), cap)
        backward = Edge(fr, len(self.graph[fr]), 0)
        self.graph[fr].append(forward)
        self.graph[to].append(backward)
    
    def bfs_level(self, s, t, level):
        q = deque()
        level[:] = [-1] * self.size
        level[s] = 0
        q.append(s)
        while q:
            v = q.popleft()
            for edge in self.graph[v]:
                if edge.cap > 0 and level[edge.to] == -1:
                    level[edge.to] = level[v] + 1
                    q.append(edge.to)
                    if edge.to == t:
                        return
    
    def dfs_flow(self, v, t, upTo, iter_, level):
        if v == t:
            return upTo
        for i in range(iter_[v], len(self.graph[v])):
            edge = self.graph[v][i]
            if edge.cap > 0 and level[v] < level[edge.to]:
                d = self.dfs_flow(edge.to, t, min(upTo, edge.cap), iter_, level)
                if d > 0:
                    edge.cap -= d
                    self.graph[edge.to][edge.rev].cap += d
                    return d
            iter_[v] += 1
        return 0
    
    def max_flow(self, s, t):
        flow = 0
        level = [-1] * self.size
        while True:
            self.bfs_level(s, t, level)
            if level[t] == -1:
                return flow
            iter_ = [0] * self.size
            while True:
                f = self.dfs_flow(s, t, float('inf'), iter_, level)
                if f == 0:
                    break
                flow += f
            level = [-1] * self.size

def main():
    h, w = map(int, sys.stdin.readline().split())
    INF = 1 << 60

    A = []
    for _ in range(h-2):
        row = list(map(int, sys.stdin.readline().split()))
        A.append(row)
    
    total_nodes = 2 * h * w + 2
    s = 2 * h * w
    t = s + 1

    dinic = Dinic(total_nodes)

    for i in range(1, h+1):
        for j in range(1, w+1):
            in_node = (i-1) * w + (j-1)
            out_node = in_node + h * w

            if i == 1 or i == h:
                cap = INF
            else:
                a = A[i-2][j-1]
                if a == -1:
                    cap = INF
                else:
                    cap = a
            dinic.add_edge(in_node, out_node, cap)

            for di, dj in [(-1, 0), (1, 0), (0, -1), (0, 1)]:
                ni = i + di
                nj = j + dj
                if 1 <= ni <= h and 1 <= nj <= w:
                    adj_in_node = (ni-1) * w + (nj-1)
                    dinic.add_edge(out_node, adj_in_node, INF)
    
    for j in range(1, w+1):
        in_node = (1-1) * w + (j-1)
        dinic.add_edge(s, in_node, INF)
    
    for j in range(1, w+1):
        out_node = (h-1) * w + (j-1) + h * w
        dinic.add_edge(out_node, t, INF)
    
    max_flow = dinic.max_flow(s, t)
    if max_flow >= INF:
        print(-1)
    else:
        print(max_flow)

if __name__ == "__main__":
    main()