import * as fs from 'fs'

// import * as readline from 'readline'
// const rl = readline.createInterface({ input: process.stdin, output: process.stdout })
// const ask = (query: string) => new Promise<string>((resolve) => rl.question(query, resolve))
// // Don't forget `rl.close()`.

const INT = Math.floor

declare global {
  interface Array<T> {
    last(): T | undefined
    isEmpty(): boolean
  }
}
Array.prototype.last = function () {
  return this.length === 0 ? undefined : this[this.length - 1]
}
Array.prototype.isEmpty = function () {
  return this.length === 0
}

const less = <T>(a: T, b: T) => (a == b ? 0 : a < b ? -1 : 1)
const greater = <T>(a: T, b: T) => (a == b ? 0 : a < b ? 1 : -1)
const bigIntMax = (...args: bigint[]) => args.reduce((m, e) => (e > m ? e : m))
const bigIntMin = (...args: bigint[]) => args.reduce((m, e) => (e < m ? e : m))
const bigIntAbs = (arg: bigint) => (arg < 0 ? -arg : arg)

declare const stdin: number
function read_stdin() {
  return fs.readFileSync(process.env.NODE_ENV === 'debug' ? stdin : process.stdin.fd, 'utf8')
}
class Input {
  readonly inputs: string[]
  private index = 0
  constructor(str?: string) {
    this.inputs = (str ? str : read_stdin()).split(/\s+/)
  }
  number() {
    return Number(this.inputs[this.index++])
  }
  numbers(n: number) {
    return this.inputs.slice(this.index, (this.index += n)).map(Number)
  }
  bigint() {
    return BigInt(this.inputs[this.index++])
  }
  bigints(n: number) {
    return this.inputs.slice(this.index, (this.index += n)).map(BigInt)
  }
  word() {
    return this.inputs[this.index++]
  }
  words(n: number) {
    return this.inputs.slice(this.index, (this.index += n))
  }
}

function array<T>(len: number, init: T): T[] {
  return Array(len).fill(init)
}

function array2<T>(h: number, w: number, init: T): T[][] {
  return array(h, 0).map(() => array(w, init))
}

type Edge = { to: number; cap: number; rev: Edge }

class Dinic {
  private level: number[]
  private edges: Edge[][]
  private edges2: Edge[][]
  constructor(private V: number) {
    this.level = Array(V)
    this.edges = [...Array(V)].map(() => [])
    this.edges2 = [...Array(V)].map(() => [])
  }
  getEdges(from: number) {
    return this.edges2[from]
  }
  addEdge(from: number, to: number, cap: number) {
    const e: Edge = { to, cap } as any
    const rev_e = { to: from, cap: 0, rev: e }
    e.rev = rev_e
    this.edges[from].push(e)
    this.edges[to].push(rev_e)
    this.edges2[from].push(e)
  }
  private bfs(s: number) {
    this.level.fill(-1)
    let q = [s]
    this.level[s] = 0
    let level = 1
    while (!q.isEmpty()) {
      const qq: number[] = []
      while (!q.isEmpty()) {
        const v = q.pop()!
        for (const e of this.edges[v]) {
          if (e.cap > 0 && this.level[e.to] < 0) {
            this.level[e.to] = level
            qq.push(e.to)
          }
        }
      }
      q = qq
      level++
    }
  }
  private dfs(s: number, t: number) {
    const iter: number[] = Array(this.V).fill(0)
    type Info = { v: number; f: number; rf: number; parent?: Info; edge?: Edge }
    const stack: Info[] = [{ v: s, f: Infinity, rf: 0 }]
    while (!stack.isEmpty()) {
      const top = stack.last()!
      if (top.v === t) {
        stack.pop()
        top.parent!.rf += top.f
        top.edge!.cap -= top.f
        top.edge!.rev.cap += top.f
        continue
      }
      let hasEdge = false
      const f = top.f - top.rf
      if (f > 0) {
        for (let i = iter[top.v]; i < this.edges[top.v].length; i++) {
          iter[top.v] = i + 1
          const e = this.edges[top.v][i]
          if (e.cap > 0 && this.level[top.v] < this.level[e.to]) {
            hasEdge = true
            stack.push({ v: e.to, f: Math.min(f, e.cap), rf: 0, parent: top, edge: e })
            break
          }
        }
      }
      if (!hasEdge) {
        if (top.v === s) return top.rf

        stack.pop()
        if (top.rf > 0) {
          top.parent!.rf += top.rf
          top.edge!.cap -= top.rf
          top.edge!.rev.cap += top.rf
        }
      }
    }
    return 0
  }
  maxFlow(s: number, t: number) {
    let flow = 0
    while (true) {
      this.bfs(s)
      if (this.level[t] < 0) return flow
      flow += this.dfs(s, t)
    }
  }
}

function main() {
  const input = new Input()

  const H = input.number()
  const W = input.number()
  const A: { i: number; j: number }[][] = [...Array(5e5 + 1)].map(() => [])
  for (let i = 0; i < H; i++) {
    for (let j = 0; j < W; j++) {
      const a = input.number()
      A[a].push({ i, j })
    }
  }

  let ans = 0
  const r_map = array(H, 0)
  const c_map = array(W, 0)
  for (let a = 1; a <= 5e5; a++) {
    if (A[a].isEmpty()) continue

    const r_set = new Set<number>()
    const c_set = new Set<number>()
    for (const { i, j } of A[a]) {
      r_set.add(i)
      c_set.add(j)
    }
    const R = r_set.size
    const C = c_set.size
    const s = 0
    const t = 1
    const g = new Dinic(R + C + 2)
    Array.from(r_set).forEach((r, idx) => {
      r_map[r] = idx
      g.addEdge(s, 2 + idx, 1)
    })
    Array.from(c_set).forEach((c, idx) => {
      c_map[c] = idx
      g.addEdge(2 + R + idx, t, 1)
    })
    for (const { i, j } of A[a]) {
      g.addEdge(2 + r_map[i], 2 + R + c_map[j], 1)
    }
    const f = g.maxFlow(s, t)
    ans += f
  }

  console.log(ans)
}

main()