#include <iostream>
#include <fstream>

using namespace std;

ifstream f("dfs.in"); ofstream g("dfs.out");
int nrc,k,a[1005][1005],n,m,viz[100003];

void dfs(int nod) {
    int i;
    viz[nod] = k;
    for(i = 1; i <= n; ++i) {
        if (a[nod][i] && viz[i] == 0) {
            dfs(i);
        }
    }
}

int main() {
    int i,j;
    f>>n>>m;
    for(i = 1; i <= 1000; ++i) {
        for(j = 1; j <= 1000; ++j) {
            a[i][j] = 0;
        }
    }
    for(i = 1; i <= n; ++i) {
        viz[i] = 0;
    }
    for(i = 1; i <= m; ++i) {
        int x,y;
        f>>x>>y;
        a[x][y] = 1;
    }
    nrc = 0;
    for(i = 1; i <= n; ++i){
        k = i;
        if (viz[i] == 0) {
            ++nrc;
            dfs(i);
        }
    }
    g<<nrc;
    return 0;
}