class FordFulkerson:
    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 dfs(self, v, t, f):
        if v == t:
            return f
        used = self.used
        used[v] = 1
        for e in self.G[v]:
            w, cap, rev = e
            if cap and not used[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
        f = INF = 10**9 + 7
        N = self.N
        while f:
            self.used = [0]*N
            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:
    N = H + W + 2
    ff = FordFulkerson(N)
    for i in range(H):
        ff.add_edge(0,i+1,1)
    for i in range(W):
        ff.add_edge(H + i + 1,N-1,1)
    for i,j in dic[a]:
        ff.add_edge(i+1,H + j + 1,1)
    ans += ff.flow(0, N-1)
print(ans)