#include <iostream>
#include <vector>
#include <stack>
using namespace std;
vector <vector <int> > graph;
vector <bool> visited;

int n,m,k;
void dfs(int vertex)
{
    if (vertex<0 || vertex>n-1) return;
    stack<int>s;
    int element,i;
    bool found;
    s.push(vertex);
    visited[vertex]=true;
    while (!s.empty())
    {
        element=s.top();
        found=false;
        for (i=0;i<graph[element].size()&& !found;i++)
        {
            if (!visited[graph[element][i]])
            {
                found=true;
            }
        }
        if (found)
        {
            i--;
            s.push(graph[element][i]);
            visited[graph[element][i]]=true;
        }
        else s.pop();
    }
}
int main()
{
    cin>>n>>m;
    graph.resize(n);
    visited.resize(n,false);
    int x,y;
    for (int i=0;i<m;i++)
    {
        cin>>x>>y;
        x--;
        y--;
        graph[x].push_back(y);
        graph[y].push_back(x);
    }
    for (int i=0;i<visited.size()&&i<n;i++)
    {
        if (!visited[i])
        {
            k++;
            dfs(i);
        }
    }
    cout<<k;
    return 0;
}