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

template<class T> istream& operator >> (istream& is, vector<T>& vec) {
    for(T& x : vec) is >> x;
    return is;
}

template<class T> ostream& operator << (ostream& os, const vector<T>& vec) {
    if(vec.empty()) return os;
    os << vec[0];
    for(auto it = vec.begin(); ++it != vec.end(); ) os << ' ' << *it;
    return os;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    int n, m, u, v;
    cin >> n >> m;
    vector<int> in(n), out(n);
    for(int i = 0; i < m; i++){
        cin >> u >> v;
        u--, v--;
        in[u]++;
        out[v]++;
    }
    ll s = 0, s1 = 0;
    for(int i = 0; i < n; i++){
        if(in[i] >= out[i]) s += in[i] - out[i];
        else s1 += out[i] - in[i];
    }
    cout << max(0ll, s1 - 1) << '\n';
}