# 整数の入力                                                                                                                            
n, m = gets.chomp.split(" ").map(&:to_i)                                                                                                
                                                                                                                                        
                                                                                                                                        
arr = Array.new(n, -1)                                                                                                                  
children_manager = Array.new(n, [])                                                                                                     
                                                                                                                                        
m.times do                                                                                                                              
  a, b = gets.chomp.split(" ").map{|x| x.to_i - 1}                                                                                      
  a_parent = arr[a]                                                                                                                     
  b_parent = arr[b]                                                                                                                     
  if a_parent == -1 && b_parent == -1                                                                                                   
    arr[b] = a                                                                                                                          
    children_manager[a] << b                                                                                                            
  elsif a_parent > -1 && b_parent == -1                                                                                                 
    arr[b] = a_parent                                                                                                                   
    children_manager[a_parent] << b                                                                                                     
  elsif a_parent == -1 && b_parent > -1                                                                                                 
    arr[a] = b_parent                                                                                                                   
    children_manager[b_parent] << a                                                                                                     
  elsif a_parent > -1 && b_parent > -1                                                                                                  
    arr[b] = a_parent                                                                                                                   
    children_manager[b].each do |c|                                                                                                     
      arr[c] = a_parent                                                                                                                 
    end                                                                                                                                 
  else                                                                                                                                  
    raise                                                                                                                               
  end                                                                                                                                   
end                                                                                                                                     
print n - arr.select{|x| x == -1}.size