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

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

    int ans = 0;
    for (int i = 0; i < N; i++)
    {
        ans += abs(inDegree[i] - outDegree[i]);
    }
    ans /= 2;
    cout << max(0, ans - 1) << endl;
}