//
//  main.cpp
//  2.B
//
//  Created by Andrey Chulkov on 7/29/15.
//  Copyright (c) 2015 Andrey Chulkov. All rights reserved.
//

#include <iostream>
#include <vector>
#include <set>
#define m_p make_pair
using namespace std;
typedef pair<int, int> int_pair;
vector<vector<int>> graph;
vector<vector<int>> inversed_graph;
vector<int_pair> edges;
vector<int> components;
vector<bool> used;
vector<int> vertecies;
int ncomp = 0;


void dfs(int v) {
    used[v] = true;
    for (auto u : graph[v]) {
        if (!used[u]) {
            dfs(u);
        }
    }
    vertecies.push_back(v);
}


void rev_dfs(int v) {
    used[v] = true;
    components[v] = ncomp;
    for (auto u : inversed_graph[v]) {
        if (!used[u]) {
            rev_dfs(u);
        }
    }
}

int main() {
    set<int_pair> condensed_edges;
    int n, m;
    cin >> n >> m;
    graph.assign(n, vector<int>());
    inversed_graph.assign(n, vector<int>());
    edges.resize(0);
    components.assign(n, 0);
    used.assign(n, false);
    vertecies.resize(0);
    for (int i = 0; i < m; i++) {
        int b_i, e_i;
        cin >> b_i >> e_i;
        graph[b_i - 1].push_back(e_i - 1);
        inversed_graph[e_i - 1].push_back(b_i - 1);
        edges.push_back(m_p(b_i - 1, e_i - 1));
    }
    for (int v = 0; v < n; v++) {
        if (!used[v]) {
            dfs(v);
        }
    }
    used.assign(n, false);
    for (int v = n - 1; v > -1; v--) {
        if (!used[vertecies[v]]) {
            ncomp += 1;
            rev_dfs(vertecies[v]);
        }
    }
    for (int i = 0; i < m; i++) {
        int u, v;
        u = components[edges[i].first];
        v = components[edges[i].second];
        if (u != v) {
            condensed_edges.insert(m_p(u, v));
        }
    }
    cout << (int) condensed_edges.size() << endl;
    return 0;
}