#include<bits/stdc++.h>
using namespace std;
using ll=long long;

int main(){
  ll n,m;
  cin>>n>>m;
  vector<vector<ll>> G(2*n);
  for(ll i=0;i<m;i++){
    ll a,b;
    cin>>a>>b;
    a--;
    b--;
    G[a].push_back(b);
    G[b].push_back(a);
  }
  vector<bool> seen(n,false);
  queue<ll> que;
  ll ans=0;
  ll rest=2*n;
  for(ll i=0;i<2*n;i++){
    if(!seen[i]){
      ll cnt=0;
      seen[i]=true;
      que.push(i);
      while(que.size()){
        ll q=que.front();
        que.pop();
        cnt++;
        for(ll u:G[q]){
          if(!seen[u]){
            seen[u]=true;
            que.push(u);
          }
        }
      }
      if(cnt%2==0){
        ans+=cnt/2;
        rest-=cnt;
      }else{
        ans+=cnt/2;
        rest-=(cnt-1);
      }
    }
  }
  cout<<rest/2<<endl;
}