# require "template"
lib C
  fun strtoll(s : UInt8*, p : UInt8**, b : Int32) : Int64
end

class String
  def to_i64
    C.strtoll(self, nil, 10)
  end
end
# require "graph/bipartite_matching"
# require "./graph"
struct Edge(T)
  property to : Int32
  property cost : T

  def initialize(@to : Int32, @cost : T)
  end

  def to_s(io) : Nil
    io << {to, cost}
  end

  def inspect(io) : Nil
    io << "->#{to}(#{cost})"
  end
end

struct Edge2(T)
  property from : Int32
  property to : Int32
  property cost : T

  def initialize(@from : Int32, @to : Int32, @cost : T)
  end

  def reverse
    Edge2(T).new(to, from, cost)
  end

  def to_s(io) : Nil
    io << {from, to, cost}
  end

  def inspect(io) : Nil
    io << "#{from}->#{to}(#{cost})"
  end
end

class Graph(T)
  getter size : Int32
  getter graph : Array(Array(Edge(T)))

  def initialize(@size : Int32)
    raise ArgumentError.new("Negative graph size: #{size}") unless size >= 0
    @graph = Array.new(size) { Array(Edge(T)).new }
  end

  def initialize(@size, edges : Array(Edge2(T)), undirected : Bool)
    raise ArgumentError.new("Negative graph size: #{size}") unless size >= 0
    @graph = Array.new(size) { Array(Edge(T)).new }
    edges.each do |edge|
      @graph[edge.from] << Edge.new(edge.to, edge.cost)
      @graph[edge.to] << Edge.new(edge.from, edge.cost) if undirected
    end
  end

  def add_edge(i : Int32, j : Int32, cost : T)
    raise IndexError.new unless 0 <= i < size
    raise IndexError.new unless 0 <= j < size
    graph[i] << Edge(T).new(j, cost)
    graph[j] << Edge(T).new(i, cost)
  end

  def add_edge_directed(i : Int32, j : Int32, cost : T)
    raise IndexError.new unless 0 <= i < size
    raise IndexError.new unless 0 <= j < size
    graph[i] << Edge(T).new(j, cost)
  end

  def [](i : Int32)
    graph[i]
  end

  def each_edge : Nil
    (0...size).each do |v|
      graph[v].each do |edge|
        yield Edge2(T).new(v, edge.to, edge.cost)
      end
    end
  end

  def edges : Array(Edge2(T))
    result = [] of Edge2(T)
    each_edge do |edge|
      result << edge
    end
    result
  end
end

class BipartiteMatching
  getter left : Int32
  getter right : Int32
  getter graph : Graph(Nil)

  def initialize(@left, @right)
    raise ArgumentError.new "Negative left vertexes size: #{left}" unless left >= 0
    raise ArgumentError.new "Negative right vertexes size: #{right}" unless right >= 0
    @graph = Graph(Nil).new(left)
    @left_match = Array(Int32?).new(left, nil)
    @right_match = Array(Int32?).new(right, nil)
    @used = Array(Bool).new(left, false)
  end

  def add_edge(l : Int32, r : Int32)
    raise IndexError.new unless 0 <= l < left
    raise IndexError.new unless 0 <= r < right
    graph[l] << Edge.new(r, nil)
    self
  end

  def add_edge(edges : Array(Edge2(Nil)))
    edges.each do |edge|
      add_edge(edge.from, edge.to)
    end
    self
  end

  private def dfs(v : Int32) : Bool
    return false if @used[v]
    @used[v] = true
    graph[v].each do |edge|
      if @right_match[edge.to].nil? || dfs(@right_match[edge.to].not_nil!)
        @left_match[v], @right_match[edge.to] = edge.to, v
        return true
      end
    end
    return false
  end

  def solve : Int32
    while (0...left).reduce(false) { |update, i|
            update | (@left_match[i].nil? ? dfs(i) : false)
          }
      @used.fill(false)
    end
    left - @left_match.count(&.nil?)
  end
end

h, w = read_line.split.map(&.to_i)
a = (1..h).map { read_line.split.map(&.to_i) }

l, r = 0, 0
edges = Array.product((0...h).to_a, (0...w).to_a).group_by { |(i, j)|
  a[i][j]
}.flat_map { |val, points|
  next [] of Edge2(Nil) if val == 0
  row = {} of Int32 => Int32
  column = {} of Int32 => Int32
  points.map do |(y, x)|
    ll = row[y]? || (row[y] = (l += 1) - 1)
    rr = column[x]? || (column[x] = (r += 1) - 1)
    Edge2.new(ll, rr, nil)
  end
}

puts BipartiteMatching.new(l, r).add_edge(edges).solve