#include <bits/stdc++.h>
using namespace std;
#include <atcoder/dsu>
using namespace atcoder;

int main() {
	int N, M;
	cin >> N >> M;
	vector<vector<int>> g( N * 2 );
	for( int i = 0; i < M; i++ ) {
		int a, b;
		cin >> a >> b;
		a--;
		b--;
		g[a].push_back( b );
		g[b].push_back( a );
	}
	vector<int> v( N * 2 );
	dsu ds( N * 2 );
	for( int i = 0; i < N * 2; i++ ) {
		if( v[i] ) continue;
		queue<int> q;
		q.push( i );
		v[i] = 1;
		while( q.size() ) {
			int u = q.front();
			q.pop();
			for( int e : g[u] ) {
				if( v[e] ) continue;
				q.push( e );
				v[e] = 1;
				ds.merge( i, e );
			}
		}
	}
	vector<vector<int>> gg = ds.groups();
	int sz = gg.size(), ans = N;
	for( int i = 0; i < sz; i++ ) ans -= gg[i].size() / 2;
	cout << ans << endl;
 }