import sys
from collections import deque

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

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.capacity > 0 and level[edge.to] == -1:
                    level[edge.to] = level[v] + 1
                    q.append(edge.to)
                    if edge.to == t:
                        return
        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.capacity > 0 and level[v] < level[edge.to]:
                d = self.dfs_flow(edge.to, t, min(upTo, edge.capacity), iter_, level)
                if d > 0:
                    edge.capacity -= d
                    self.graph[edge.to][edge.rev].capacity += 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
        return flow

def main():
    input = sys.stdin.read().split()
    idx = 0
    H = int(input[idx])
    idx += 1
    W = int(input[idx])
    idx += 1
    
    A = []
    for _ in range(H-2):
        row = list(map(int, input[idx:idx+W]))
        idx += W
        A.append(row)
    
    INF = 10**18
    S = 2 * H * W
    T = S + 1
    dinic = Dinic(2 * H * W + 2)
    
    dirs = [(-1,0), (1,0), (0,-1), (0,1)]
    
    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 dx, dy in dirs:
                ni = i + dx
                nj = j + dy
                if 1 <= ni <= H and 1 <= nj <= W:
                    nin_node = (ni-1)*W + (nj-1)
                    dinic.add_edge(out_node, nin_node, INF)
            
            if i == 1:
                dinic.add_edge(S, out_node, INF)
            
            if i == H:
                dinic.add_edge(in_node, T, INF)
    
    max_flow = dinic.max_flow(S, T)
    if max_flow >= INF:
        print(-1)
    else:
        print(max_flow)

if __name__ == "__main__":
    main()