#include <iostream>
#include <fstream>

using namespace std;

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

int main() {
    int n,m;
    int a,b;
    int k;
    bool igz=false;
    fin >> n >> m;
    int S=n;
    int v[n+1];
    for (int i = 0; i <= n; ++i) {
        v[i]=i;
    }
    for (int j = 0; j < m; ++j) {
        fin >> a >> b;
        k=v[a];igz=false;
        for (int i = 1; i <= n; ++i) {
            if(v[i]==k){v[i]=b;igz=true;}
        }
        if(igz==true)S--;
    }
    fout << S;
}