#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,m,n) for(int i=m; i<n; ++i)
#define repl(i,m,n) for(ll i=m; i<n; ++i)

vector<vector<int>> Graph;
vector<bool> visited;

void dfs(int v, int &cnt){
    visited[v] = true;
    cnt++;
    for(int nv : Graph[v]){
        if(visited[nv]) continue;
        dfs(nv, cnt);
    }
}

int main(){
    int N, M;
    cin >> N >> M;

    Graph.resize(2*N);
    rep(i, 0, M){
        int A, B;
        cin >> A >> B;
        Graph[A-1].push_back(B-1);
        Graph[B-1].push_back(A-1);
    }

    visited.assign(2*N, false);
    int cnt = 0, ans = N;
    for(int i = 0; i < 2*N; ++i){
        if(visited[i]) continue;
        dfs(i, cnt);
        ans -= cnt / 2;
        cnt = 0;
    }
    cout << ans << endl;

    return 0;
}