import sys
input = sys.stdin.readline

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

# dinic法

from collections import defaultdict,deque

V=H*W*3+2
start=V-2
goal=V-1

EDGE=[defaultdict(int) for i in range(V)]

now=H*W
for i in range(H):
    L=defaultdict(list)
    for j in range(W):
        if A[i][j]!=0:
            L[A[i][j]].append(i*W+j)

    for l in L:
        EDGE[start][now]=1

        for x in L[l]:
            EDGE[now][x]=1000000

        now+=1

for j in range(W):
    L=defaultdict(list)
    for i in range(H):
        if A[i][j]!=0:
            L[A[i][j]].append(i*W+j)

    for l in L:
        EDGE[now][goal]=1

        for x in L[l]:
            EDGE[x][now]=1000000

        now+=1

ANS=0
while True:
    # まずBFSする

    DIS=[-1]*V
    Q=deque([start])
    DIS[start]=0
    EDGE2=[[] for i in range(V)]

    while Q:
        x=Q.popleft()
        for to in EDGE[x]:
            if EDGE[x][to]==0:
                continue
            
            if DIS[to]==-1:
                DIS[to]=DIS[x]+1
                Q.append(to)
                EDGE2[x].append(to)
                
            elif DIS[to]==DIS[x]+1:
                EDGE2[x].append(to)

    if DIS[goal]==-1:
        break

    # BFSしたときのEDGEを使ってDFSする

    MINCOST=[float("inf")]*V
    NOW=start
    ROUTE=[-1]*V
    
    while NOW!=-1: # DFS

        cost=MINCOST[NOW]
        
        if NOW==goal:
            ANS+=cost
            i=goal
            
            while i!=start: # goalからたどり,Routeを使ってEDGEの更新
                j=ROUTE[i]
                if EDGE[j][i]==cost:
                    NOW=j
                    EDGE2[j].pop()
                
                EDGE[j][i]-=cost # 使ったルートをいけなく更新
                MINCOST[j]-=cost                
                EDGE[i][j]+=cost # 逆向きに進めるようにする.
                i=j
            continue

        if EDGE2[NOW]:
            to=EDGE2[NOW][-1]
            ROUTE[to]=NOW
            MINCOST[to]=min(cost,EDGE[NOW][to])
            NOW=to

        else:
            if NOW==start:
                break
            EDGE2[ROUTE[NOW]].pop()
            NOW=ROUTE[NOW]
            

print(ANS)