#include <iostream>
#include <fstream>
#include <vector>
#define NM 100002
using namespace std;

vector <int> gr[NM];

int n, m, i, a, b, v[NM], nrc, tv;

void dfs(int n)
{
    v[n] = 1;
    tv++;
    for(auto j:gr[n])
        if(v[j] == 0)
            dfs(j);
}

int main()
{
    ifstream fin ("dfs.in");
    ofstream fout ("dfs.out");
    fin >> n >> m;
    for(i = 1; i <= m; i++)
    {
        fin >> a >> b;
        gr[a].push_back(b);
        gr[b].push_back(a);
    }
    while(tv < n)
    {
        for(i = 1; v[i]; i++);
        dfs(i);
        nrc++;
    }
    fout << nrc;
    return 0;
}