#include <stdio.h>
#include <vector>
using namespace std;

vector <int>lv[100000];
vector <int>::iterator ii;
long eticheta[100000];

int main()
{
    FILE *f=fopen("dfs.in","r");
    FILE *g=fopen("dfs.out","w");
    int i,n,m,x,y,nr=0;
    fscanf(f,"%d%d",&n,&m);
    for(i=1;i<=m;i++)
    {
        fscanf(f,"%d%d",&x,&y);
        lv[x].push_back(y);
        lv[y].push_back(x);
    }
    for(i=1;i<=n;i++)
        eticheta[i]=i;
    for(i=1;i<=n;i++)
        for(ii=lv[i].begin();ii!=lv[i].end();++ii)
            if(eticheta[ii]<=eticheta[i])
                eticheta[i]=eticheta[ii];
            else eticheta[ii]=eticheta[i];
    for (i=1;i<=n;i++)
        if(eticheta[i]==i) nr++;
    fprintf(g,"%d",nr);
    return 0;
}