#include <iostream>
#include <fstream>
#include <vector>
using namespace std;

const int maxi = 100000;
vector<int> lista[maxi];
int vizitat[maxi], componente = 0;

void DFS(int nod) {
    if(vizitat[nod] == 0)
        componente++;
    vizitat[nod] = 1;
    for(int i : lista[nod])
        DFS(i);
}

int main() {
    ifstream fin("dfs.in");
    ofstream fout("dfs.out");
    int n, m, x, y;
    fin >> n >> m;
    for(int i = 0; i < m; ++i) {
        fin >> x >> y;
        lista[x].push_back(y);
    }
    DFS(1);
    fout << componente;
    return 0;
}