class UnionFind
  def initialize(n)
    @size = Array.new(n, 1)
    @rank = Array.new(n, 0)
    @parent = []

    (0..n).each do |i|
      @parent[i] = i
    end
  end

  def find(x)
    if @parent[x] == x
      x
    else
      @parent[x] = find(@parent[x])
    end
  end

  def unite(x, y)
    x = find(x)
    y = find(y)
    return if x == y

    if @rank[x] < @rank[y]
      @parent[x] = y
      @size[y] += @size[x]
    else
      @parent[y] = x
      @size[x] += @size[y]

      @rank[x] += 1 if @rank[x] == @rank[y]
    end
  end

  def same?(x, y)
    find(x) == find(y)
  end

  def size(x)
    @size[find(x)]
  end
end

N, M = gets.split.map(&:to_i)
Q = N.times.map { gets.split.map(&:to_i) }
C = Hash.new { |h, k| h[k] = [] }

Q.each do |b, c|
  C[c] << b
end

ans = 0
uf = UnionFind.new(M + 1)

C.each do |c, pos_list|
  pos_list.each_cons(2) do |a, b|
    next if uf.same?(a, b)

    ans += 1
    uf.unite(a, b)
  end
end

puts ans