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

ifstream in("dfs.in");
ofstream out("dfs.out");

const int maxn = 100001;
vector<int> vecini[maxn];
int visited[maxn];
int k = 1, n, m;

void dfs(int nod)
{
    stack<int> st; st.push(nod);
    while (!st.empty())
    {
        int top = st.top();
        st.pop();
        visited[top] = k;
        for (int i = 0; i < vecini[top].size(); i++) st.push(vecini[top][i]);
    }
    for (int i = 1; i <= n; i++)
        if (visited[i] == 0) { ++k; dfs(i); break; }
}

int main()
{
    int x, y, first = 0;
    in >> n >> m;
    for (int i = 0; i < m; i++)
    {
        in >> x >> y;
        if (first == 0) first = x;
        vecini[x].push_back(y);
    }
    dfs(first);
    out << k;
    return 0;
}