# Dinic's algorithm
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())
A = [list(map(int,input().split())) for _ in range(H)]

dic = {}
AF = set() #存在する値のセット
for i in range(H):
    for j in range(W):
        a = A[i][j]
        if a in dic:
            dic[a].append([i,j])
        else:
            dic[a] = [[i,j]]
        AF.add(A[i][j])
if 0 in AF:
    AF.remove(0)
AF = sorted(AF,reverse = True)
ans = 0

for a in AF:
    Vs = dic[a]
    setH = set()
    setW = set()
    for i,j in Vs:
        setH.add(i)
        setW.add(j)
    H1 = len(setH)
    W1 = len(setW)
    B = sorted(list(set(setH)))
    dicH = dict(zip(B, range(len(B))))
    B = sorted(list(set(setW)))
    dicW = dict(zip(B, range(len(B))))
    for i in range(len(Vs)):
        Vs[i][0] = dicH[Vs[i][0]]
        Vs[i][1] = dicW[Vs[i][1]]

    N = H1 + W1 + 2
    dinic = Dinic(N)
    for i in range(H1):
        dinic.add_edge(0,i+1,1)
    for i in range(W1):
        dinic.add_edge(H1 + i + 1,N-1,1)
    for i,j in Vs:
        dinic.add_edge(i+1,H1 + j + 1,1)
    ans += dinic.flow(0, N-1)
print(ans)