n, m = gets.chomp.split(" ").map(&:to_i)
hash = Hash.new(0)
count = 0
arr = []
n.times do
    b, c = gets.chomp.split(" ").map(&:to_i)
    arr << [b,c]
    # count += 1 if hash[c] >= 1
    # count -= 1 if iru[c] == b && hash[c] >= 1
    # iru[c] = b
    # hash[c] += 1
end
arr = arr.uniq

arr.each do |i,j|
    count += 1 if hash[j] >= 1
    hash[j] += 1
end
puts count