#include <queue>
#include <iostream>
#include <vector>

struct Station {
    Station():marked(false){}
    bool marked;
    std::vector<int> children;
};
std::vector<Station> stations;
std::vector<bool> isSource;
std::vector<bool> isCollector;
int source = 0, collector = 0;

unsigned count_pipes(const int st, const unsigned pipes) {
    if (stations[st].marked)
        return 0;
    if (st != collector)
        stations[st].marked = true;
    if (st == collector)
        return pipes;
    unsigned result = 0;
    for (auto station : stations[st].children)
        result += count_pipes(station, pipes + 1);
    return result;
}

int main() {
    int N, M;
    std::cin >> N >> M;
    for (int i = 0; i < N; i++)
        stations.push_back(Station());
    for (int i = 0; i < N; i++) {
        isSource.push_back(true);
        isCollector.push_back(true);
    }
    
    for (int i = 0; i < M; i++) {
        int s, t;
        std::cin >> s >> t;
        s--;
        t--;
        stations[s].children.push_back(t);
        isSource[t] = false;
        while (!isSource[source]) 
            source++;
        isCollector[s] = false;
        while(!isCollector[collector])
            collector++;
    }
    std::cout << M - count_pipes(source, 0) << std::endl;
}

/*
5 6
2 4
3 5
2 5
1 4
2 3
5 1
*/

/*
4 4
1 2
1 3
2 4
3 4
*/