#include<iostream>
#include<algorithm>
#include<stack>
#include<vector>
#include<set>

using namespace std;
using ll = long long;

#include<atcoder/dsu>

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    
    int n,m;
    cin>>n>>m;
    vector<int> cnt(n,0);
    set<int> s;
    atcoder::dsu uf(n);
    vector<vector<int>> g(n);
    for(int i = 0;i<m;i++){
        int u,v;
        cin>>u>>v;
        u--;v--;
        uf.merge(u,v);
        s.insert(u);
        s.insert(v);
        cnt[u]++;
        cnt[v]--;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    int sum = 0;
    int all = 0;
    int c = 0;
    vector<int> vis(n,0);

    for(int i = 0;i<n;i++){
        if(vis[i]) continue;
        if(uf.size(i)==1&&s.count(i)==0) continue;
        int tmp = 0;
        vector<int> que;
        que.push_back(i);
        vis[i]++;
        for(int j = 0;j<que.size();j++){
            int ni = que[j];
            if(cnt[ni]>0) tmp += cnt[ni];
            for(auto&to:g[ni]){
                if(vis[to]) continue;
                vis[to]++;
                que.push_back(to);
            }
        }
        tmp = max(0,tmp-1);
        all += tmp;
        c++;
    }
    cout<<all+c-1<<endl;

}