import sys
input = sys.stdin.buffer.readline
sys.setrecursionlimit(10 ** 7)
U = 5 * 10 ** 5 + 1


class BipartiteMatching:
    def __init__(self, N, M):
        self.N = N
        self.M = M
        self.pairA = [-1] * N
        self.pairB = [-1] * M
        self.edge = [[] for _ in range(N)]
        self.was = [0] * N
        self.iter = 0

    def add(self, s, t):
        self.edge[s].append(t)

    def _DFS(self, s):
        self.was[s] = self.iter
        for t in self.edge[s]:
            if self.pairB[t] == -1:
                self.pairA[s] = t
                self.pairB[t] = s
                return True
        for t in self.edge[s]:
            if self.was[self.pairB[t]] != self.iter and self._DFS(self.pairB[t]):
                self.pairA[s] = t
                self.pairB[t] = s
                return True
        return False

    def solve(self):
        res = 0
        while True:
            self.iter += 1
            found = 0
            for i in range(self.N):
                if self.pairA[i] == -1 and self._DFS(i):
                    found += 1
            if not found:
                break
            res += found
        return res


H,  W = map(int, input().split())
P = [[] for _ in range(U)]
for i in range(H):
    for j, a in enumerate(map(int, input().split())):
        P[a].append((i, j))

ans = 0
for i in range(1, U):
    if not P[i]:
        continue
    X, Y = zip(*P[i])
    xtoi = {x: j for j, x in enumerate(sorted(set(X)))}
    ytoi = {y: j for j, y in enumerate(sorted(set(Y)))}
    match = BipartiteMatching(len(xtoi), len(ytoi))
    for a, b in P[i]:
        match.add(xtoi[a], ytoi[b])
    ans += match.solve()
    # print(i, match.solve())

print(ans)