#include <iostream>
#include <fstream>
using namespace std;
ifstream f("dfs.in");
ofstream g("dfs.out");

struct nod{
    int inf;
    nod *leg;
};
typedef nod *pnod;
nod *v[100001], *p, *q;
int n,m,x,y,nr,viz[100001];

void citire()
{
    f>>n>>m;
    for(int i=1;i<=m;i++)
    {
        f>>x>>y;
        p=new nod;
        p -> inf = x;
        p -> leg = v[y];
        v[y] = p;

        q= new nod;
        q -> inf = y;
        q -> leg = v[x];
        v[x]= q;
    }
}

void dfs(int i,int j)
{
    nod *z;
    viz[i]=j;
    for (z = v[i]; z != NULL; z = z -> leg)
        {
            if (viz[z -> inf]==0)
                dfs(z -> inf,j);
        }
}

int main()
{
    int j;
    citire();
    for(int i=1;i<=n;i++)
        if(viz[i]==0)
        {
            j=i;
            nr++;
            dfs(i,j);
        }
    g<<nr;

    return 0;
}