#include <bits/stdc++.h>
#include <vector>
#define NMAX (int)(1e5 +5)

using namespace std;

int n, m, x, y;
vector<int> g[NMAX];
bool viz[NMAX];

void DFS(int x) {
    viz[x] = true;
    for (int y : g[x])
        if (!viz[y]) DFS(y);
}

int main()
{
    freopen("dfs.in", "r", stdin);
    freopen("dfs.out", "w", stdout);

    scanf ("%d %d", &n, &m);
    for (int i = 1; i <= m; ++i) {
        scanf("%d %d", &x, &y);
        g[x].push_back(y);
    }

    int compCount = 0;
    for (int i = 1; i <= n; ++i)
        if (!viz[i]) {
            ++compCount;
            DFS(i);
        }

    printf("%d\n", compCount);
    return 0;
}