import sys
from collections import deque
sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


class Dinic:
    def __init__(self, N, inf):
        self.N = N
        self.inf = inf
        self.G = [[] for _ in range(N)]
        self.level = [0]*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):
        self.level = [-1]*self.N
        deq = deque([s])
        self.level[s] = 0
        while deq:
            v = deq.pop()
            lv = self.level[v] + 1
            for w, cap, _ in self.G[v]:
                if cap > 0 and self.level[w] == -1:
                    self.level[w] = lv
                    deq.appendleft(w)

    def dfs(self, v, t, f):
        if v == t:
            return f
        for e in self.iter[v]:
            w, cap, rev = e
            if cap > 0 and self.level[v] < self.level[w]:
                d = self.dfs(w, t, min(f, cap))
                if d > 0:
                    e[1] -= d
                    rev[1] += d
                    return d
        return 0

    def flow(self, s, t):
        flow = 0
        while True:
            self.bfs(s)
            if self.level[t] == -1:
                return flow
            *self.iter, = map(iter, self.G)
            f = self.inf
            while f > 0:
                f = self.dfs(s, t, self.inf)
                flow += f


H,W = MI()
A = [LI() for _ in range(H)]

X = [[] for _ in range(5*10**5+1)]
for i in range(H):
    for j in range(W):
        a = A[i][j]
        X[a].append((i,j))

ans = 0
inf = 10**18
for i in range(1,5*10**5+1):
    if not X[i]:
        continue

    A = set()
    B = set()
    for h,w in X[i]:
        A.add(h)
        B.add(w)

    A = list(A)
    B = list(B)
    lA = len(A)
    lB = len(B)

    Di = Dinic(lA+lB+2,inf)
    S = lA+lB
    T = lA+lB+1
    dic_A = {}
    dic_B = {}
    for j in range(lA):
        dic_A[A[j]] = j
        Di.add_edge(S,j,1)
    for j in range(lB):
        dic_B[B[j]] = j+lA
        Di.add_edge(j+lA,T,1)

    for h,w in X[i]:
        Di.add_edge(dic_A[h],dic_B[w],1)

    ans += Di.flow(S,T)

print(ans)