#include <bits/stdc++.h>

using namespace std;
using ll = long long;

struct UnionFind {
    int ngroup, N;
    vector<int> par;
    vector<int> siz;

    UnionFind(int _n) : par(_n), siz(_n), N(_n) {
        ngroup = _n;
        for(int i = 0; i < N; i++){
            par[i] = i;
            siz[i] = 1;
        }
    }

    int root(int x) {
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }

    int unite(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        if (rx == ry) return rx;
        ngroup--;
        if (siz[rx] > siz[ry]) swap(rx, ry);
        par[rx] = ry;
        siz[ry] += siz[rx];
        return ry;
    }

    bool same(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }

    int size(int x){
        return siz[root(x)];
    }

    int group_count(){
        return ngroup;
    }

    vector<vector<int>> groups(){
        vector<int> rev(N);
        int nrt=0;
        for (int i=0; i<N; i++){
            if (root(i) == i){
                rev[i] = nrt;
                nrt++;
            }
        }
        vector<vector<int>> res(nrt);
        for (int i=0; i<N; i++){
            res[rev[root(i)]].push_back(i);
        }

        return res;
    }
};

int main(){
 
    int N, M, x, y;
    ll ans=0, cnt;
    cin >> N >> M;
    UnionFind tree(N+1);
    vector<int> in(N+1), out(N+1);
 
    for (int i=0; i<M; i++){
        cin >> x >> y;
        tree.unite(x, y);
        out[x]++;
        in[y]++;
    }
    
    vector<vector<int>> g = tree.groups();
    for (auto &x : g){
        bool f=0;
        cnt = 0;
        for (auto y : x){
            if (in[y] != 0) f=1;
            cnt += abs(in[y]-out[y]);
        }
        ans += max(0LL, cnt/2-1) + f;
    }

    cout << ans-1 << endl;

    return 0;
}