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

class UnionFind
{
    int n;
    vector<int> parent;
    vector<int> edgeCnt;

public:
    UnionFind(int n_) : n(n_)
    {
        parent.resize(n);
        edgeCnt.resize(n, 0);
        iota(parent.begin(), parent.end(), 0);
    }
    int find(int x)
    {
        int y = parent[x];
        if (y != parent[y])
        {
            y = find(y);
        }
        return parent[x] = y;
    }
    void unite(int a, int b)
    {
        int x = find(a);
        int y = find(b);
        if (x != y)
        {
            parent[y] = x;
            edgeCnt[x] = edgeCnt[y] + 1;
        }
        else
        {
            edgeCnt[x]++;
        }
    }
    bool same(int a, int b)
    {
        return find(a) == find(b);
    }
    int EdgeCnt(int i)
    {
        return edgeCnt[i];
    }
};

int main()
{
    int N, M;
    cin >> N >> M;
    vector<int> u(M), v(M);
    vector<int> inDegree(N, 0);
    vector<int> outDegree(N, 0);
    UnionFind uf(N);
    for (int i = 0; i < M; i++)
    {
        cin >> u[i] >> v[i];
        u[i]--;
        v[i]--;
        inDegree[v[i]]++;
        outDegree[u[i]]++;
        uf.unite(u[i], v[i]);
    }

    vector<int> cnt(N, 0);
    for (int i = 0; i < N; i++)
    {
        cnt[uf.find(i)] += abs(inDegree[i] - outDegree[i]);
    }
    int ans = -1;
    for (int i = 0; i < N; i++)
    {
        if (uf.find(i) == i)
        {
            if (uf.EdgeCnt(i) > 0)
            {
                ans += max(0, cnt[i] / 2 - 1);
                ans++;
            }
        }
    }
    cout << ans << endl;
}