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

using namespace std;

const int N_MAX = 1e5 + 1;

vector <int> graph[N_MAX];
stack <int> stk;
vector <bool> visited;

int edgesAdded = 0;
int unvisitedNodes;


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

void DFS(int node)
{
    int head = stk.top();

    for(auto neighbor: graph[head])
    {
        if(visited[neighbor] == true)
        {
            continue;
        }

        stk.push(neighbor);
        visited[neighbor] = true;
        DFS(neighbor);
    }

    stk.pop();
}

int main()
{
    int n, m, x;

    fin >> n >> m;

    visited.resize(n + 1);
    fill(visited.begin(), visited.end(), false);

    for(int i = 0, st, dr; i < m; i++)
    {
        fin >> st >> dr;
        graph[st].push_back(dr);
        graph[dr].push_back(st);
    }

    for(int i = 1; i <= n; i++)
    {
        if(visited[i] == true)
            continue;

        edgesAdded++;
        visited[i] = true;
        stk.push(i);
        DFS(i);
    }


    fout << edgesAdded;

    return 0;
}