#include <iostream>
#include<vector>
#include<fstream>

using namespace std;
int n,m;
vector<vector<int> > graph;
vector<bool> visited;
void dfs(int vertex)
{
    if(vertex<0||vertex>n-1)
        return;
    vector<int> s;
    int element;
    unsigned int i;
    bool found;
    s.push_back(vertex);
    visited[vertex]=true;
    while(!s.empty())
    {
        element=s.back();
        found=false;
        for(i=0;i<graph[element].size()&&!found;i++)
        {
            if(!visited[graph[element][i]])
            {
                found=true;
            }
        }
        if(found)
        {
            i--;
            s.push_back(graph[element][i]);
            visited[graph[element][i]]=true;

        }
        else
        {
            s.pop_back();
        }
    }
}
int main()
{
    ifstream f("dfs.in");
    f>>n>>m;
    graph.resize(n);
    visited.resize(n,false);
    int x,y;
    for(int i=0;i<m;i++)
    {
        f>>x>>y;
        x--;
        y--;
        graph[x].push_back(y);
        graph[y].push_back(x);
    }
    int nr=0;
    for(int i=0;i<visited.size()&&i<n;i++)
    {
        if(!visited[i])
        {
            dfs(i);
            nr++;
        }
    }
    ofstream g("dfs.out");
    g<<nr;
    f.close();
    g.close();
    return 0;
}